As I said earlier in this thread, I saw the RotS blu-ray projected onto a 100"+ screen at my relatives' place and it was mind-blowing just how three-dimensional the movie already is. If they take their time and don't screw up the conversion, they've got their work cut out for them.
The only problem, as has been stated, are people's memories of the movie itself, memories kept fresh in our minds by Mr. Plinkett's reviews.
People will turn out in significant numbers and pay actual money to see the OT-SE in 3D in theaters (not me). That's how much good will those movies have earned.
The prequels will always be the prequels.
At least they've already gotten Episode I out of the way.
A 3D re-release of the OT is an inevitability at this point. Titanic and Jurassic Park have already gotten that treatment. Just the other day it was announced the 3D conversion of Wizard of Oz will screen in September. Ya think Disney and Lucasfilm wouldn't want to add Star Wars to the list and finally knock Gone with the Wind from its #1 all-time adjusted box office record?
So, the only question now is how they roll it out. I'm sure they'll figure out something.
Also, with all-day franchise marathons in theaters becoming a thing now (Avengers, Dark Knight Rises and Twilight all did it last year), I'm betting we'll see something similar happen the day before Ep7's release (again, count me the hell out).
The only other big question is how Disney and Fox will work things out.
It's my NSHO that 20th Century Fox should at the very least have perpetual theatrical distribution rights to any existing or future Star Wars movie with "Episode" in the title. The thought of an Episode VII without that fanfare is kinda depressing, honestly.