I don't know if Locker will be an elite guy, but if he doesn't perform at a high level this year he is gone and they can start looking for better options. I just don't see Dalton as an elite level QB, I see him as a career middle tier guy that doesn't have the skillset to carry a team to a SuperBowl victory.
Do you see Dalton as being in the upper echelon of quarterbacks in the league? Where would you rank him? I am not saying he is a terrible quarterback, just that he is closer to a Fitzpatrick or Shaub than he is to a Rodgers or Brees.
Also I am reading your question as in if you trade Locker for Dalton you are going all in with Dalton because you believe he can get you a Superbowl victory. Not that you think he is a better prospect than Locker, I wouldn't argue that at this point in their careers Dalton is the better prospect, just not a guy I would want to build a franchise around, I also believe unless Locker plays at a high level this year the team will move on and draft his replacement, and I'd personally rather take the gamble that the team could get a guy with a higher ceiling than Dalton.