Regarding the zones, as long as they continue the overall improvements they've implemented last year, I'm pretty open to any theme, and any sequel zone does offer the chance of improving over predecessors.
As a preface, I'm amusing the themes mentioned, though it really does sound like these were tossed out of nowhere on discord, so heavy grain of salt with that.
Vamp: '55 was widely celebrated, and rightly so. The casts really played with the theme and each other to make for a great atmosphere and interactions. Meanwhile '85: New Years Eve, didn't have the same bite. It was a neat concept and I did enjoy the show for the first time, as well as the 80's celeb Vamps, but that zone relied solely on the show as there really wasn't much else beyond it. (It also suffered from not being big enough for New York.)
Vanity Ball: When it comes to the first one, I liked the concept, LOVED the soundtrack, but it wasn't fully there. Like with Vamp '85, this one was really focused on the little shows and runway, and not much beyond that. It didn't help this zone was devoid of scares, especially with chunks of the cast standing around and talking with each other. (And I think I recall this zone suffered the worst from that during that time.)
Give either of these zones the improvements and an energetic cast that's focused on scaring, and we can have something good. I can see either of them returning at some point, but I don't know if they'd do two sequel zones in the same year...though I wouldn't mind being proven wrong on that!
As for the Rainforest idea, sure, why not? Watch this be the one that happens since it's a totally new theme for them.