I actually hope it's based off of the GBA version rather than the DS version. I know a lot of people didn't like what they did at the end of the GBA version but I liked having the option. Porom actually ends up as a better healer than Rosa.
Well, there's always the option that it will be based off of the original, but with all of the improvements made to later versions, I'd doubt it. 1 and 2 PSP were based off of the GBA version, so here's to hoping.