Realistically, the set list would be something like this;

Meddle -
One Of These Days

Dark Side of the Moon -
Breathe
Time
Money
Us and Them
Brain Damage/Eclipse

Wish You Were Here -
Welcome to the Machine
Wish You Were Here
Have a Cigar (Maybe)

I don't think they would have anything from Animals, but if they did, they'd probably only do Sheep.

The Wall -
Another Brick in the Wall Pt 2
Empty Spaces/Young Lust
Comfortably Numb
Run Like Hell

The Final Cut -
The Final Cut

And if they do anything from the early era;
Astronomy Domine
Bike

And if they did anything from the post-Waters era;
Learning to Fly
High Hopes

The Career mode would probably have them playing some famous gigs like......

Earls Court (1973, 1981, 1994)
Pompeii (1971)
Knebworth (1975, 1990)
Venice (1989)
UFO Club (1966)
Royal Albert Hall (1969)
Olympic Stadium in Montreal (1977)

They'd probably be in chronological order, starting with the UFO Club and ending with Earls Court in 1994. It would go through the band's history like The Beatles Rock Band. It'd also be nice if they got the master tracks from some of those gigs, like Pompeii and Earls Court 1994. In fact, even getting the studio master tracks will be a challenge. Since the Beatles Rock Band had about 45 songs, I'll write up what I think the setlist for Pink Floyd Rock Band would be like. Tracks will slashes will probably be one whole track on the game in order to make the songs flow.

Dark Side of the Moon:
Speak to Me/Breathe/On The Run
Time/Breathe Reprise
Great Gig in the Sky
Money
Us and Them/Any Colour You Like/Brain Damage/Eclipse

Wish You Were Here:
Shine On You Crazy Diamond parts 1-5
Have a Cigar
Wish You Were Here

Animals:
Sheep

The Wall:
The Whole thing. No exceptions. All 26 tracks. Some tracks combined. Everybody's gonna want it.

Post Waters:
Learning to Fly
High Hopes

Pre DSOTM:
One of These Days
Echoes (Maybe)

Syd:
Astronomy Dominie
Arnold Layne
See Emily Play.

That should be good enough for one game. Anything else will be DLC.

If they did make it, it would be freaking awesome in so many ways