Any game-dev putting out another game in under four months time is almost 100% assuredly reusing assets. Unless they're some kind of prodigy, I wouldn't get hopes up for much new art or animation wise.
Based on his last work, and how the game is described on ci-en, basically he split the game into several parts. Running the same engine, combat, jump arcs etc. will all be the same. Nothing gameplay wise will be touched, if it is, maybe some balance stuff. It's all new girls and levels. Less of a new game, more of an expansion. Hence why the first game is referred to as world 1, and this one is world 2.
Enemies from world 1 will return, but the game will feature 25 new girls to accompany them.
If you dont mind being spoiled, 20 of the new girls were already revealed on his blog.
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Also, game has been delayed until mid september. To satiate our curiosity he posted a pic of the new harpy girl. The new *new*. Guess what boys. Its cowgirl style! we fuckin' did it, we're in like Flynn! Yeah! haven't seen that one before!