My biggest hope is for at least one more multiball. One main multi in the pro just isn't enough these days (edit: two I guess...forgot about retro KNIGHT multi...which is AWESOME...but my point remains). I would love for them to incorporate Catapult Multi into the pro....even if it is just something like every 10 ramp shots = 1 lock (or every 10 left "orbit" VUK shots? You could easily look at the VUK as being a catapult...).
Otherwise maybe multiple levels for each enemy area, with the second (third?) battle in each area being a multi? I find it interesting that the inserts are labeled for the area (Burning Sands, Deep Freeze, etc) rather than named for the enemy you battle there (Sandworm, Lich Lords, etc). I am hoping that means more battles are planned for each area rather than just one enemy. That would be a great place to bring more multiball modes, depth, etc into the game.
I really fell in love with this one at MGC, as did my 11 year old daughter and even my wife. My daughter clearly preferred it over Wonka, Monster Bash, AFM, etc. I was surprised, but it was one of her highlights of the show. Mine too.