He wouldn't be all that happy being third as say De Gea who is an up and coming keeper or Lopez who would be contend as he is less notable. Valdes has years of experience and it would be a shame for a player who's won the champions league to be sitting on the bench next to a second choice keeper.
and Valdes will always be a great keeper who never played for his national side, well Catalunya isn't part of FIFA, anyway Valdes is still relatively young, we see keepers playing for national sides in their late 30s, so next WC if he maintains this consitency i'm sure he could have a say for first if not second, which is more dignified than third.