So here's my prediction for what will lead to some big picture resolution near the end of the series, not that I want it to end: at some point it's going to be revealed that the Revolutionaries have undercover operatives in both the Marines and the World Government at various levels of power and influence.
Oda has shown deep cover is very much a part of the world he's created, most recently with the SWORD unit. Drake is a Marine, posing as a pirate. We've already seen the curious case of Kuma, a Revolutionary undercover as a pirate, and mysteriously giving himself over to the World Government. And we've seen rebellious or reformed Nobles: Sabo, Doflamingo, Mjosgard. Although some Revolutionaries are openly known, I'd be surprised if there aren't any that have infiltrated the Government or Marines.
This would make for very satisfying resolution, because it's hard to square the atrocities of the World Government with some of the likeable characters who seem to support it, and the answer will be they have been planning to bring it down all along. Although, I do think some of these characters may still be illusioned by the Government.
I don't think I'll be right about all of these, or that this will be all of them, but here's who I think is a secret Revolutionary:
Vegapunk (programmed pacifistas and Kuma to turn on the Government)
I'm not sure there will be any pirates included here, because I'm not sure what the Revolutionaries would gain, now that the Shichibukai system is gone, although they may choose to ally with them for their own benefit. If pirates are included I could see Shanks included here, but I'm not sure about any others.
Anyways, would love to hear some other thoughts, if you think this is where things are headed or nah.