I think their upside is a unit like this: C: Tim Duncan PF: Chris Bosh SF: Gerald Wallace SG: Brandon Roy PG: Tony Parker Obviously, everyone's not going to reach their upside...but having an upside like that is amazing to me. They can miss that by a wide margin and still be a perennial championship contender.
You realize that Roy is already "near" a scoring leader at 7th in the league, right? He is also already at 5+ assists and 5rbs per game. This is his 3rd year in the league. If the stats you posted are what you believe it would take for Roy to win the MVP, he doesn't have far to go.
Lebron doesn't have his "Scottie" though (yet?) As for Andre Miller, it's all hearsay at this point but I've been on the Sixers forum at RealGM.com in the past and apparently there have been public comments either from Dre or his agent stating that he'd like to finish up his career back on the West Coast. Take that for what it's worth