I have always felt that Matt deserved a WHC title run. Back in 2005(?) he had an awesome feud with Edge where in my opinion he out performed Edge, he has always been super over with the crowd and was good enough in the ring to be a champ. I know he is more beat up and not in the best shape anymore but I don't see why a 1-2 month reign would hurt anything. They did it with Kahli, Christian and Mysterio after all!
Put Matt on SD and make him a top guy.
As far as Jeff goes He will be a main eventer either way. Vince may be pissed about how he left the company but the fact is that he would be a great investment. He sells merchandise and tickets. What more do you want in a wrestler?
They could have a pretty decent feud with Kane/Bryan as well.
I have always been a Matt fan so I may be a little biased, but I always felt that out of the Hardys, Edge/Christian and the Dudleys Matt was the better wrestler(not recently though).
Who knows, they are both getting older and their bodys are starting to fail them. Maybe they both want one last run with a big Paycheck before they retire. WWE would be the best way to do that, they wrestle for 2 more years, retire in their late 30's/early 40's, get one last big paycheck and go out in a memorable way. Not a terrible idea if they are up for it.