Other people using AutoTune isn't what burned T-Pain out, it was giving all those hooks away. From what Jamie Foxx said, Blame It was actually a T-Pain solo.....I've also heard that Low was given to Flo Rida as well. When you're on 20 hooks between each album dropping, it's going to be hard to get people to anticipate your solo work. With the exception of I'm Sprung, he never had a big solo hit single. Silver & Gold, plus Rap Song (Ross didn't need to be on that, IMO) were both very slept on, though.
Future, I think took people by surprise. It's not often you find a trap rapper who uses AutoTune. I slept on his music for the longest, I messed with a few tracks, but I didn't check for his solo work until the past few months or so. His 2nd album will tell the tale, either he'll continue to grow, or this moment in time will go down as his peak.