i just copied this and thought it was interesting.

Is it Brooke, Peyton, or Lindsay going to Vegas with Lucas?
We have confirmed that in the first episode there will be a lot of “dream” scenes.
A lot of rumored spoilers are going around it’s Peyton… however… all 3 girls will be filming a scene that places them going to Vegas with Lucas.
So… it’s still up in the air as to which girl it will ACTUALLY be.
Since Michaela McManus (”Lindsey”) got a lead role on Law & Order: SVU… we can pretty much rule her out.

and it's also just been said that it costs too much to go to vegas, so everything will be on set....
but i don't know how reliable that is.
:)