Arsenal can sign better talent. He's considered by experts to have nearly reached his prime already, so I'm not surprised that Wenger wanted to offload him to a club that is dumb enough to overpay for his services.
Well, we have a few young defenders coming up. (Hoyte, Song, Traore, Djourou, plus Silvestre, and Wenger may be looking for one more defender)
Good luck to him. Wenger does it again. If he were to leave full-time he Arsenal would have got £8m for him