I'm not really seeing it. If you look at Espionage Act cases that involve the actual passing of classified information (rather than, say, intimidating socialists and anarchists), just about everyone gets convicted. Ellsberg and Russo might have been able to rely on public sentiment but charges against them were dismissed. Snowden's position is much weaker.
He'll likely get convicted. The US would be happy to put him on trial.
>If they bring him home for a secret trial, the risk rioting or a martyr
Secret trial? Rioting? I think you're overestimating general support for Snowden and have some odd ideas about the way the justice system works.