Is there a possibility of having even more and bigger belly sizes in the future?
Bigger sizes and more stages in between are planned, but are not next in line on the development chain. Right now I'm looking to make sure the game doesn't slow down with lots of 'friends' active, maybe translating to tick-based calculation instead of per-frame calculation, and thinking about what gameplay content to add in next. (It might be something... sloshy. No promises.)