Yes you read it right! There's gonna be a sequel to one of the greatest (or practicly the first) crossover film there is!
I just wanted to take a look at 'Who framed Roger Rabbit' fan art on google on my iPod, and there it was. By natural instinct I click it and hear it reads;
"An up-coming film and sequel to The first 1988 film 'Who framed Roger Rabit' which takes place in to current time, almost 70 years after Marvin Acme's murder in 1947. At the opening in this film there will be a new boss of the Maroon Cartoon Studios but in fact he is the brother of Judge Doom and wants revenge on Eddie Valient, Roger Rabbit and the other toons. So Eddie, Roger, and Jessica must stop him before it's to late!"
I read the description in the character file and it says that there will be a lot of cartoon from 1980 till 2012 in the movie and most of the will play roles in the film than being cameos.
But it doesn't say when it'll in theaters but if you wanna see the many characters go to Wikipedia now!