20th Century FOX rep has stated that the sequel to Dragonball Evolution (Dragonball 2 Reborn) could in fact still happen. When asked if they have forgotten about DB Evolution and any possible sequels, they had this to say.
Not necessarily. It could happen. Who knows? We have Wall Street 2 coming out this year, and the first one was 20 years ago!
It has been over a year since the film initially released in the US and we have yet to hear any official confirmations. Take this as a rumor for now, but consider the fact that the sequel is still planned (until we hear otherwise).