Personally, I'd like to see a Super Mario Galaxy 3 for the Wii U. There's so much that can be done with the gravity effects, there's no reason to stop the series.
Surely they would support the Wii U Pro controller as well, so for those who would rather play with a traditional controller can.
A second player could play as a Luma using the gamepad. They could move anywhere on their own instead of constantly following Mario, still stunning enemies and picking up items.
Maybe even have a two-player mode, separate from the story mode, where player 2 can play as Luigi on the gamepad. There could be co-op levels, battle modes, etc.

Personally I think they should put a Halt in the galaxy series. SMG2 felt too much of a rehash.

No no no no no no no no no no no no no no no no no no no no no no no no no

That was all typed by hand.

I'd be up for that.
I wasn't too excited leading up to Galaxy 2 due to the fact that I was expecting just more of the same... but it ended up somehow managing to be so much more fun than the (already amazing) first game, so if Nintendo still have more ideas then sounds good to me.
I'd be pretty happy with any 3D Mario platformer on the Wii U though, Galaxy or not.

not happening

no more galaxys 1 was anough then there was a 2nd im already sick of the new super mario bros i just want a new mario 3d platformer

But with galaxy they can make the stages ANYTHING. They just need to change the engine up. Bring back the punch / grab from Super Mario 64. Make powerups last until you get hit, instead of being timed. Make Mario small when he only has 1 HP. Keep powerups from level to level and be able to carry powerups in your inventory, like Super Mario Bros. 3. And have a variety of cool powerups. Bring back the frog suit.
Also, forget what I said about player 2 playing as a Luma. Add a second player who plays as Luigi and can join in or drop out at any time.

The Galaxy games are done with...chances are the theme will be different, maybe a Sunshine sequel or something entirely new, I dunno.

I want something with more open worlds like Super Mario Sunshine.

...You know what, just give me Sunshine 2.

Nope.

I personally want something similar to Mario 64 or Sunshine.

I loved both games, but I think they should move on.

Super Mario Universe.

Add those suggestions of making power ups permanent and carrying powerups and making Mario small. Then add the physics and art style of the Galaxy games. Make a bunch of levels with challenges based around certain power ups or requirements- for example, they could make a later level force you to be small for the whole level, providing Poison Mushrooms at the start, for an insane challenge. Heck, I would actually like to see a 2D based level with the Pull Star gimmick. The possibilities are endless!

Meh I want to see a new 3D mario game in general.

Why do people want Nintendo to continue to be unoriginal with the Mario series? The Mario series is losing its creativity and I'd rather the series didn't carry on like that. Super Mario galaxy and its sequel are two of the best games ever and SMG2 managed to feel unique more than NSMBW did but we don't need a third one. The next 3D Mario platformer should be an original game. I also hope that the next 3D Mario platformer isn't in the style of SM3DL.

Yes definitely. This should have been a launch game. Nintendo needs to complete a Super Mario Galaxy trilogy. SMG2 is possibly the best game of ALL time so it's mind boggling to think what they can do with number 3. It will be stupid to abandon the series.

I seriously hope not bad enough their over milking NSMB without a 3rd Galaxy title.

Yeah because the story is so important here. I'm not sure what I'll do if they don't tell us what happens after Galaxy 2.

Super Mario Sunshine 2: The Dark Il Piantissimo Rises

Galaxy is a very well thought out Mario series and it works really well, I'd definitely like to see more of it but to be honest... I wouldn't mind seeing something new with the series. NSMB2 is a step in that direction, sort of...

I wouldn't mind having a more open world kind of game though... explore the mushroom kingdom from one edge to the other, kind of like Mario 64 I suppose.

Think of the possibilities...