PT If Dooku had killed Anakin, what was Sidious's backup plan?

If Dooku had by an unforeseeable stroke of luck killed Anakin in ROTS, did Sidious have a backup plan?

Dooku is elderly so unsuitable for Imperial enforcing duties and is a threat to Sidious because he remains idealistic about the New Order and could conceivably want to be Emperor (or at the very least, Imperial Chancellor) himself.

Palpatine likely knew that Padmé was pregnant (at the very least, he knows that Anakin fears for her life and that she is his wife so I wouldn't be surprised if he was aware that she was expecting) so I imagine, had Dooku killed Anakin, that Palpatine would have kept him as an apprentice, taken over the galaxy, and then taken Luke and Leia from Padmé, killed her, and raised her children to take Dooku's place.

There's nothing in ROTS that Anakin does that Dooku couldn't conceivably do (heck, the clones alone probably could have attacked the Jedi temple). Thus, Dooku would have stayed at Palpatine's side until he wore out his welcome and then Luke or Leia would have taken over. Also, with Obi-Wan dying on board the Invisible Hand as well, Palpatine and Dooku likely would have been able to defeat Yoda and thus eliminate the Jedi altogether.

I think they both would have tried to betray each other

Dooku I think wanted an apprentice of his own and Sidious knew ofthe dangers of that.

Dooku was a means to an end to Sidious until he found someone "younger and more powerful"

If Anakin had died, it would have demonstrated that he was not worthy to be Palpatine's apprentice.

If Anakin died then whoever made that prophecy should be sued!

Padme was was already pregnant, so he'd done his part

I still see no reasons to believe that Palpatine knew that Padme was pregnant. He wanted all of the Jedi killed that is Order 66. If Palpatine knew they were alive why would he pay no attention to Padme. He is in the Senate Chamber with her when he proclaims the Republic as the First Galactic Empire. He just let her leave there. We know this because she is seen boarding her ship going to find Anakin on Mustafar.
Another reason to believe he did not know is because he needed/wanted younger apprentices as Palpatine mentions he will soon have a new apprentice who is far younger than Dooku.

If Dooku had killed Anakin he most likely would have kept Dooku around until he had found a more suitable replacement for him. Palpatine was always one step ahead of everyone so it would not be surprising if he had something prepared for just such a situation. It is interesting that Lucas chose the name "Invisible Hand" as the Flag Ship for Dooku in Revenge of the Sith.

Multiple meanings, definitely (also, given the libertarian political idealism that Dooku uses to entice the members of the CIS in the AOTC script/novelization) ... but I thought it was Luceno who came up with that name?

Anyway, to answer the OP: IMO, Palpatine was likely too self-confident to have a backup plan.

Dooku was the back up plan. When he made Anakin duel Dooku, he was testing the strength of both.

Says who?

Normal behaviour for a Sith.

If Dooku managed to kill Anakin, who's to say that there isn't some other wayward Jedi disillusioined from the clone wars who would become a good apprentice?

Palpatine never refers directly to Padme's pregnancy but with the close watch he needed to keep on Anakin I'm sure he had spies and was aware if the pregnancy. He left her alone because as long as she was alive he had something to use to control Anakin.

Palpatine appeared quite pleased to tell Anakin she was dead. Let us remember that neither of them knew about Leia until the end of Jedi My thouhhts on letting her leave are he just did not need her anymore.

First, the babies Padme carries were not Jedi. Their no threat to Palpatine at the moment so letting Padme live a little longer is not that big of a deal. Plus, killing Padme would really piss off his new apprentice which is not what Palpatine wants.

Second, given how much Palpatine seems to know about Anakin and Padme's relationship (i.e. marriage, the fact that Anakin is worried about Padme dieing). And the fact that it's not exactly hard to see that Padme is pregnant at the end of RotS. I have to believe that someone as smart as Palpatine would be able to deduce that Anakin is the one who knocked up Padme.

They were force sensitives. As long as a force sensitive exist there is a posibility for more Jedi. This is why the younglings were killed. They were not Jedi either. Palpatine also foresaw Luke turning to the darkside and we kniw how that turned out.

Force sensitive yes, but years and years away from posing any threat to him. Not to mention Palpatine's dealing with a lot of things at the moment. He's destroying the Jedi, turning the Republic into an Empire, destroying the Confederacy, and the training of a new apprentice. Maybe he was planning on killing her in a week . Just because he didn't kill her from the word go doesn't prove that he didn't know she was probably pregnant with Anakins child. Also, I reiterate, killing the wife of your newly turned apprentice would be a great way to get a lightsaber in your back. The younglings are Jedi in so much as they have some Jedi training. They have the basics. If one of them survived, they could have conceivably restarted the Order which is why Palpatine had them killed. No offense but you can't (or more accurately I should say you shouldn't) use the fact that the audience knows something as an arguement. Palpatine believes he is always right. And until Luke, he was.

My point is this why would he let her go when he has her right there? It makes little sense to let her go free when he has her there. What I am saying is not speculationnor is it an argument as it is there on the screen. He let her go. It is also stated in Jedi that if it were known by Anakin that he had any offspring they would be in danger. The thing is Anakin already knew about the baby. As protective as Anakin was if.Palpatine went near Padme Im sure he woud have seen Anakin at his highest level of intensity.

Yes, if Anakins offspring had grown up (which of course they did) they would be a threat to him. But that's if they grow up. A week old child is no threat to Palpatine. And in Palpatine's mind he is proven correct when a short time after letting her go, she's dead and so is the child (at least as far as he knows). What i'm saying is that while Palpatine does want to kill all the Jedi, just because he doesn't kill Padme (or at least her baby) the first opportunity he gets doesn't mean that he wasn't planning on it or won't.

If Dooku killed Anakin, I think the Emperor would train multiple Sith, ignoring the rule of two and built an army of Sith and hide them for the right moment,
lets say Order 66.

I always try to remember that these children are not just any force sensitive children. These are children of the Chosen One. Their Force potential would be through the roof even as children. It appeared that if Palpatine knew they were alive he would have either tried to train them when they were ready as he did Darth Maul or he would have them killed.

What better back up plan would there be than to have the children of the Chosen One learn the ways of the darkside from birth? Anakin was already planning on removing Palpatine as he told Padme that he and her could rule the galaxy together. If Palpatine was aware they were alive and let Padme go he made a very, very big mistake.

Well Episodes 4,5,6 won't happen as we know them... But I think Palpatine would have stopped Dooku before then.

A bit off topic but how soon can you tell if someone is pregnant with Force-sensitive babies? Why wouldn't the Jedi have known that Padme was pregnant? If the babies were Force-Sensitive wouldn't the Jedi or Palpatine be able to sense them in the womb?

"The Emperor knew, as I did, that if Anakin were to have any offspring, they would be a threat to him..." Obi-Wan Kenobi, ROTJ