Well, I hate to burst your bubble, but from what I've heard, InnocuousGames isn't going to make a sequel to it. But that doesn't mean that somebody else isn't able to. Please make sure a LOT of developers know this.
Prouckt:Bounty Run IS a survival mode.
Also, Amorphous+ was the sequel to the original Amorphous on Newgrounds. So, it should be an Amorphous ++, or Amorphous (Triangle Symbol), since that's the sign for Delta, the third letter in the Greek alpahbet, and it has three sides.