The cat is out of the bag, really catching snowden at this point is just to serve as an example for others, not in strategic value of its own...
China already has whatever they wanted from snowden,
Russia already has whatever they wanted from snowden,
Encrypted copies of his data are in the hands of probably dozens of journalists and ambasadors,
and the story is already on the news...
And if they wanted to make an example of Snowden, the last place they want him is in an American court of law, with cameras and stuff. Gitmo or some other extra-legal incarceration isn't much better, if it's public.
The best example would be for him to be disappeared. Let his encrypted secrets come to light, so it's obvious that he's either dead or getting tortured somewhere, and that the American government simply doesn't care about diplomatic niceties when it comes to silencing whistleblowers. That would be a lesson to the wary.
China already has whatever they wanted from snowden, Russia already has whatever they wanted from snowden, Encrypted copies of his data are in the hands of probably dozens of journalists and ambasadors, and the story is already on the news...