Proven himself? No, nononononoono. Skyfall may have had it's fun moments, but the writing was not one of it's best points. We have supposed professional and experienced characters make totally moronic decision that almost rivals that of Prometheus stupidity. And to give credit to John Logan alone is pretty drastic when you consider the fact that two other writers wrote this film and Logan was brought in to make changes, and his changes are so obvious.
John Logan is not so much a writer who can write stories on his own, he's a writer who works to indulge the people he works with. With Nemesis being dictated as a Picard and Data storyline, he pretty much writes the movie as though Data and Picard are the only characters who matter, and like in Generations, there should be moments where the actors can indulge themselves in things that we've never seen their characters actually do. Kirk LOVES to ride horses (since when?) and Picard LOVES to ride four wheeled cars (since when?).