Three new houses would be fantastic. My first experience was last year, and I had a splendid time; their newer house designs meet and exceed the standards of HHN's showmanship and shatter its standards of scare factor.
If they're replacing three houses, then my votes would be Ultimate Gamble, Nevermore, and Blood Asylum - but the latter is still relatively new so they'd probably get rid of Zombie Mortuary first (as great as it is). If they only replace two, I hope it's Gamble and Nevermore.