I agree with Rob, and think the timing is right and it's a good chance for someone else, despite being a Liverpool fan I would also go for John Terry.
Beckham has been a good captain and showed a great pride in playing for his country, I don't think he had a fantastic world cup but he wasn't the only one.
For free kicks and crosses there is no-one better, however the modern game requires someone with a bit more flair and the ability to go past defenders which is not David's game.
He is England through and through - many young kid's look up to him.