You have to wonder how Superman will disguise himself if science advances to the point of people no longer needing to wear glasses (or the need to wear them for long).
My Prediction: Clark will wear a visor. And what will his reasons for wearing the visor be? Easy, he'll claim that his eyes are very sensitive to all forms of light. Kind of like the real reason the Eradicator wore his visor during the "Death/Return" storyline.
Interesting point, NotSuper. Superman's been around for 60 years, and the first sixty years are always the hardest, so we ought to see Superman around for a good long time. Might be interesting to dust this post off years from now and see if you were right.
Though I don't know about the idea of glasses becoming obsolete. First off, laser surgeries are pretty spooky: hey, I read science fiction, I know what laser beams can do, and I'm not letting some quack zap me in the eyeballs. Nossir! And I'm sure a lot of people with visual defects feel the same way.
Plus, as a glasses wearer myself, I would continue to wear glasses simply because glasses make me look intelligent and distinguished, which is the sort of image I want to project to people that don't know me. Glasses are a style statement as much as they are a means of correcting visual problems.