Unless Shelton is deep in Chateau Bow Wow, he has a future, but not as a first choice starter (at least not for a few years, and not unless he improves a lot). He is useful as an offensive sub off the bench, a role he filled very well last year, no matter how much certain posters want to forget it. He can run at tired legs, deliver good balls into the box, receive a cross and win balls in the air in midfield.
I suspect that other teams might find him more useful, however, so a trade is certainly possible. Trouble is that if he really is still hurt, we aren't moving him this summer.