I doubt it. He has been driving for the most successful F1 team in history for 3 seasons now and he's been having motivation problems ever since Massa took the lead in 2008, despite him winning WDC the season before. Given what he has stated since it is clear he won't be driving for Ferrari next year, indicates that he is somewhat unhappy with the Massa love which is understandable. That's through his personality and own lack of PR skills though. Would this be better at McLaren where Hamilton is the clear favorite?
Not a chance. He might be competitive for a while, but sooner or later, I wouldn't be surprised to see him fall back similarly as he has to Massa. It's not his skill which is the problem, it's his motivation and evidently lack of interest.
I think people hoping for a top performing Kimi at McLaren are getting their hopes up a bit too high on this one. He's never really shown us that hunger for success as we've been seeing from Hamilton, Alonso, even Massa.