The use of the word "remix" in the potential game's title would suggest that the new game is based on material from the first two; i.e. remixed content instead of entirely original material. But we don't know more than that -- and, since that was just an extrapolation based on the title, we don't really know anything. Though we might expect more Scribblenauts, which seems like a good thing. We've typed out an email to WB to try to summon some answers.