Many have said that changes need to be made to the old films to make them fit in better with the prequels. Even with the prequels happening first, even if people are meant to view them first, this is backwards. The original films were made first, hence they established the continuity that the prequels must follow. In fact, Lucas has been following this approach all along. Ewan McGregor was picked for his resemblance to Alec Guinness. I don't see Lucas recasting old Obi-Wan to resemble the younger one. The triangular shapes of the Jedi Starfighters, Obi-Wan's beard, the lightsaber designs, the appearances of many characters, especially Owen, Beru, Anakin, Padme, Mon Mothma, are all designed to resemble what was established in the old trilogy, not as an excuse to butcher the old films to fit the new ones.