That's very much along the lines of my theory. I've always thought that Moridin will possibly realize that (to coin a phrase from Brandon Sanderson) it's all about "journey before destination," and that the inevitability of the DO winning isn't a reason to make that ending come any sooner. Remember, Moridin isn't selfish anymore, he's nihilistic. Then, due to this revelation will use the link with Rand to switch bodies with him, causing Moridin to sacrifice himself so that Rand may live.