From what I have read, these are facts:
- He was not working for a foreign government
- He did not reveal the info for money
- He concluded that his agency was breaking the law
- He was selective about what he revealed
- He went public at a great personal cost
...and he made public illegal activity by public officials ( breach of everyones 4th amendment rights ), so he is a whistleblower and should be protected. The senators that were briefed and approve of this should stand trial for conspiring to commit civil rights violations along with the NSA, FISA court judges, and the President.
There exists a classified whistle blower process. Essentially, it allows someone inside a classified program to contact an investigative agency that has individuals cleared for access to the program.
Snowden does not appear to have used this process. A claim to be a "whistleblower" will be difficult to sustain in the face of this.
The basic problem is that what he did _was_ illegal. It was also morally the right choice.
The judicial branch is not well set up to handle that. The executive branch will want to hang him high. The legislative branch will run around in circles, as always.
Snowden's best bet is to become very hard to find and wait for the next US President to issue him a pardon.