I think he definitely has it in himself to take another championship if the opportunity presents itself, but I think this year has shown one important thing: he can’t fall too far behind too quickly, or the pressure becomes too much for him.
I think if you compare his impressive 2007, 2008 and 2010 drives to this year’s, the biggest difference is that the pressure to score is much much higher this year. In those years, just scoring points regularly would put you in a good position to win the championship, but with Vettel just winning every other race, Hamilton is pushing and pushing for every single point to keep a glimmer of hope, and in that, he pushes too far.
I think that’s one difference between Vettel (since late 2010) and Hamilton: when he needs to perform, Vettel keeps his cool and brings home the points, as we’ve seen by his last few races in 2010. When the pressure to perform is that badly on Hamilton, he pushes himself into mistakes; not even that many, but enough to miss the target.