Leave it to Oliver Stone to jump on a controversial, polarizing political subject. Snowden seems like the kind of thing Stone would pounce on.
JGL doesn't look anything like Snowden, IMO, but I think he's a good enough actor for that to not really matter.
I'm curious how Stone would portray Snowden. Depending on who you ask, he's an unfairly persecuted heroic whistleblower, or a security-compromising traitor, or somewhere in between (which is usually where the truth actually lies).