I just had a thought: Don has effectively pissed off and/or betrayed just about everyone in the office except Roger (the last two seasons anyway) and shown such ruthless intent to go business first, that I wouldn't be surprised if he gets devoured down the line. That goes for his personal life as well, as the people who don't despise him right now would if they knew the truth. Especially in the event that something happens concerning his past as we have been anticipating. Would someone tip off the fact that Don deserted to destroy him and get the chance at usurping his position?
I really think Don is going to get screwed by the end of the season worse than he ever has before. I can't see how he won't be. We've already seen him blab to Trudy just because he was mad, what would really keepihim from destroying Don should he be given the opportunity?
Personally, I can't see that happening. Which is not to say that it couldn't, but the problem is that Don is essentially the most important person in the agency. Without him they're nothing. Like, literally. He's the only one that matters. Practically everyone else is expendable. Now, that might change a little with the merger, but I can't see it changing by much. Everyone knows who Don Draper is, and everyone knows he has amazing ideas. If Pete took down Don in that fashion, he'd essentially destroy the agency in the process. He better have a bunch of money set aside first.
A caveat: I will say that an interesting ending for the series would be for Don to flee New York -- his life, his family, his career, whatever -- and create a third identity. I don't think this is a likely outcome because he's too old now, but thematically that would be an interesting conclusion to it all, and one way that might be set up is if his past life is somehow revealed and he has to go into hiding yet again.
I'm tempted to say the whole "we're going to reveal your dirty secret to everyone!" arc is done. It comes up every once in a while (i.e. the lighter), but only for Don. I think that's a demon that he has to carry with him forever, and I'm not entirely sold on the idea that it's suddenly going to come out and cause a crisis. I haven't seen any foreshadowing for that, but if somebody has I'd be interested in what the hints might be.