I was there last week and it's still empty. Nothing going on there at all. I agree it would make a huge massive maze for Haunt if they did that.
Another thing about Knott's I can't figure out when I was there: Why have a Johnny Rocket's, and a couple of buildings down Coasters grill? They look almost exactly alike, and almost offer the same thing. Seems a waste to me.
There was a rumour Perilous PLunge was leaving, and if that happens, combined with the old Dnosaurs building, it would free up lots of space.