James is too ....... old to win a MotoGP title. If he was his age and had already 5-6 seasons under his belt, it would be another question, but he is 27-28 and only a rookie. He should win some races, but a title? Nope.
I compare him to a bit more talented Colin Edwards. Came over in their late 20's after kicking ... in WSBK, but had and will have some trouble being a top tier rider in MotoGP. Their struggles is a not because of a lack of abilities on the bike, but more that years on a production based bike is very different that a MotoGP machine. They have to change their riding styles and at their age, they have a habit and it will be hard to change.