That's a great point about Panama. The advantage was, of course, that they hyped up Cirie like crazy and so there was just generally more hype around the episode, which is half the battle, so the same sort of hype would need to be generated in this case, but structurally speaking I guess it proves the point that it's feasible.Exile Island did that.
Well, technically the Cirie/Danielle fire making challenge happened at the stat of the episode, but for all intents and purposes they had a final three for the finale, with Terry winning an advantage in a reward challenge.
I doubt Survivor wants to go down that route again, but it's possible that medevac could force their hands.
Anyway, I don't necessarily think there will be another medevac. I mean, people have definitely speculated about it (and Joe seems like a reasonable assumption). But I fear for the show, and my own viewing party, if we get another dud like the Neal exit.... (which I personally liked though because of the deep human emotion, but a lot of people were underwhelmed).
What baffles me is how they could have made a much bigger deal out of the Caleb exit. Maybe flesh out some more of the camp life beforehand. I guess they felt they had no choice since it was the Reward challenge so basically nothing would have happened for the first 2/3rd of the show.