Where ever you heard that from is wrong. It's basically been confirmed that filming will take place this year and I really wouldn't be surprised if the script was already written. And it would be harder to turn it into two movies than to just leave it as one because virtually nothing of substance actually happens in the 2nd half of the book. They would just stand there, talk to Aro, avoid a stand off and go home. It would be the most boring movie ever. So don't worry, it'll be produced unless Summit suddenly goes bankrupt which is practically impossible due to the success of the last two mives :)