It seems Sidious doesn't like Ahsoka too much, and it's the perfect opportunity to turn Anakin further down the Dark Side. If Maul kills Ahsoka, Anakin will hunt him down in vengeance and slaughter him without adhering to the tenets of the Jedi Code. For me, it seems likely that 1 or both of Maul + Ahsoka need to die for continuity. So, I'm betting both will die and Sidous will be the puppet master behind it as usual. If events go according to plan, it will explain a lot about ROTS and also it matches Anakin's personality. The seeds of the Dark Side are slowly sprouting in him even during the Clone Wars.