"To be honest I cannot see this escalating much further. There will probably be some humiliating mock trial/confession for the media to boost internal morale in Iran, then they will be released."
I agree.
As we're chatting here the US and Britain are probably negotiating through their diplomats for the release of the intelligence agents. But I doubt they will be released w/o an arms lenght exchange.
What intelligence agents are you talking about? The sailors and Marines were part of a routine patrol that inspects ships for smuggling activities. They had just finished inspecting a dhow, so we're not even talking about inspecting anything very significant in the shipping world. And they just were in rubber rafts, so it wasn't really a high-risk seizure (since the Iranians were pretty confident that there'd be no attempt to stop them).
As for the Iranian intelligence agents, they were captured in Iraq; and the one who defected, if that's what happened, is certainly not going back.
I don't think there'll be any "exchange," but on the other hand, I don't think this is going to be a major crisis. It's just a typical part of Iranian behavior, and we have tolerated this kind of thing for nearly 40 years now, so there's no reason to expect a change. They'll get some propaganda value out of it and then realease the sailors.