I doubt that any "major" names will move.. Trust me, if John Cena was going to Smackdown, they would've put that on RAW and not a Supplemental Draft... As for Smackdown being without a Champion, look at last year's draft... WWE Champion Triple H was drafted to Smackdown and World Champion Edge stayed put... So RAW was without a Champion...Edge then defeated Batista and Triple H defeated John Cena to swerve the fans..Then, the next night on Raw, new RAW Superstar CM Punk cashed in his Money in the Bank briefcase, defeated a beaten up Edge, and bam, the World Championship's back on RAW.
Now, things will obviously have to be done differently this time as last year, Night of Champions featured TWO World Title, Raw vs SD matches so either Title change would mean a Title coming to Raw... Not this year.. If Triple H loses the WWE Title to Randy Orton(and I fully expect he will), nothing is solved as both Triple H and Randy Orton are now on Raw.. So that only leaves John Cena's World Championship so it's pretty much a foregone conclusion that Edge's 9th World Title reign will begin at Backlash... Now they could always swerve fans and have CM Punk cash in his briefcase on Randy Orton, based on their history, after he defeats Triple H but that'd be nearly impossible with Legacy lurking around.. Plus it'd kill any momentum Orton had and kill any momentum of a potential McMahon or Batista heel turn that's pretty much inevitable at this point.
All in all, My safe assumption is that we'll leave Backlash with Rated RKO standing atop the WWE as I expect Edge to reign as World Heavyweight Champion, eventually turning face and feuding with Chris Jericho, and Randy Orton to reign as the WWE Champion, feuding with either Triple H, John Cena, or Batista(if he stays face which I doubt)