Also, If he hadn't stayd his ruling, the NSA would have rushed to the appeals court and gotten an emergency stay. And it would have been granted too. By staying his own ruling, he is just doing the reasonable thing. Whatever the collective opinion of slashdot, this is a ruling that would require a substantial change on (relatively) longstanding POLICY. The appeals court WILL want to look at this. They will write opinions. They may send it back to him on a technicality, but it will go back to the appeals court again either way. It WILL be appealed to the supreme court.
Staying his ruling gives his opinion a better chance of standing on appeal. He appears reasonable, decisions by unreasonable people are easy to overturn, & the reverse is true as well. And I'm sure even appeals judges remember if they have to miss an important event to rule on an emergency stay made necessary by an unreasonable judge.
Failing to stay the ruling would have been a dick move and would not have made any diference. Unfortunately.