well,...
look at 'The Matrix', they've created 2 movies at the same time,... and the LOTR, 3 movies... I don't think it would be so uncommon anymore, and it's easyer that way,.. face it, you have everyone and all the tool at hand, why not?
I gues "the Shrek people" took the same route... :p
true it is or not, either way,.. more movies for us and more money for them!!... lol