yeah, that sounds about right. All the actors have to lend their likeness and voices to anything else involved with the franchise, i.e. video game as well, so that's also part of the contract. Whether or not they'll actually BE in any subsequent movies is up to the director and writers and stuff...
Nightcrawler was supposed to be *in* the movie, but because his role was so small they deemed it not worth the time to put on the make up and to spend for the FX and everything.
