This is the exact reason why Shelton is on ECW. The WWE understands that he is an amazing talent and is as frustrated with his inability to get over the the crowds as we are, so they put him on a 3rd rate television show to allow him to push the new talent. I believe that when this feud is over, Sheamus is going to get a nice rub whether he wins OR loses.
And I definitely agree with Xfear (as usual) by saying that Shelton would make a very good ECW champion. His mic skills are still a bit sub-par, but his face turn seems to be helping his crowd reaction. I think that if he was able to capture the ECW title many internet fans would be happy and he would make ECW a smarky show to watch.
As for Sheamus, like I said, win or lose, this guy is going to make a name for himself once this feud is over. If it goes well, he should be able to jump to Smackdown within the next 3-6 months, in my opinion. The WWE doesn't seem to be wasting time in moving ECW talents up to the premier television shows (i.e. Jack Swagger). They're desperate to make new stars and I'm sure they can't wait to roll the dice on Sheamus.