Well, he is good. And it doesn't matter if he's linked with a move away only after his WC games, same goes for Claudio Bravo, who has signed for Barca only after this WC, although everyone knew he was great last year when he helped Real Sociedad to reach CL.
And he is only 27 years old, how is that "almost 30"? If he keeps up this tempo, he can play for another 10 years. And really? Is this the first time ever a player has a small clause, gets bought and continues to deliver top class performances? It's football, you can buy David Luiz for 50M or Keylor Navas for a few millions, buy out clause indicates nothing about his quality as a goalkeeper.