Now, we've heard about the possibility of a Dragonball Evolution sequel before, but all we really knew was that the actors had been signed on for two sequels-- which doesn't mean they'll get made, it's really more a “just in case” for any series that could become a major movie franchise, which Warner Bros. clearly thinks DBE could.
But Goku actor Justin Chatwin chatted up the UK's SciFiNow and made it known that there's actually a script to a sequel already written, and it takes the film back into the “genealogy of Dragonball,” apparently. Now, I think of Goku as the start of the genealogy, since he's the one who has kids, but...eh. At this point, I'm lacking the energy to complain.
Anyway, a script existing does not guarantee a sequel-- they'll only greenlight it if the first film's returns suggest that a sequel would do well. That said, what do YOU think this sequel would be about? You guys know DBZ better than me, probably.