Doubt it will happen, unless it's downloadable.

Putting together a full game is rather expensive, especially when it comes to producing and distributing the product. Harmonix doesn't have EA anymore to pay the bills. Microsoft is paying for the distribution of Dance Central 3 simply because it's one of the most profitable Kinect games out there.

The core Rock Band games are... less profitable. Quite simply, the physical games don't sell nearly as well as the Dance Central games, so it would be a terrible business move to fund a sequel by themselves. So unless they plan to change the integrity of the game and change the entire gameplay style to cater to Microsoft's Kinect boner, I doubt Microsoft will be throwing money at them.

But what about Mad Catz? Haha! Good joke...

I actually see RB4 coming out as basically a $60 DLC pack. That would be interesting, even if new things couldn't really be added. It would all be Grohl.

My very first sentence agree with you...

If RB4 is just like Bliz but a core RB game Ill be 100% fine with that.

I know, I was just agreeing through repetition.

I honestly just like it when new games come out because, along with the whole 80 songs for 60 bucks business, we also get songs that wouldn't come out any other way.

Close to what I was going to say.

I doubt I'll get much out of Blitz gameplay. It'll be a straight track pack for me, (at a decent price) since I'm so used to playing the instruments. I just never cared for track-switching games of this type.

If they release multiple versions of Blitz and keep the swap-out of music going, I won't be too upset about the lack of RB4.

EDIT

At this point I doubt we'll ever see a full sequel to RB3. It could happen, but on top of the problems Splnyc mentioned, all the instruments are also getting very scarce. It would take one hell of breakthrough game to generate the necessary demand for them to restart instrument manufacture. And even more to get retailers to carry them again.
I do hope I'm wrong though.

http://www.youtube.com/watch?v=VsHE_ZIEyq4

Also, I'm in the downloadable RB4 camp.

HAXX

I'm OK with this.

http://www.youtube.com/watch?v=61iJLdgzgck
OMFG! O_O

He also has a FC of Prelude/Angry Young Man. WTF.

Call me when he FC's Veil of Illumination. Of course, I don't have any reason to be judgmental. The only song I've ever FC'd on Keys is Need You Tonight.

Helen Wheels is the best keys song ever

You're so wrong, totally Machinehead.

This game needs more trill lanes and disco flipping with inconsistent kicks

We need another Hautewerk pack.

Please keep in mind Part 2 has never been FC'd even on legacy.

There should be a Green Day Rock Band 2

Hows about a third Nickelback pack.

Ill sooner buy Justin Bieber's discography.