Speculation is speculation. And speculation is fine for what it is. But don't put too much stock in it.
And everything that's been said about why Punk left has been just that: speculation. This has been said on here before (by others and me, including, I think, earlier in this thread), but Punk, HHH, and VKM are the only guys who have the first real clue why Punk walked out. And none of those guys are talking publicly about it (Vince has even told WWE stockholders, people he's not allowed by law to lie to, that Punk is on "sabbatical").
I'll take the words/ideas expressed by Paul Heyman on SCSA's podcast as the closest thing to gospel we're likely to get:
When Austin asked Heyman for his insight, Heyman said that he had received "a couple of perspectives" about what happened in that meeting (he refused to elaborate, but I would venture to guess that one of them was Punk's and the other one was probably HHH's, but that's a complete coin flip) and that as long as those three men remain silent about it, nobody will really know what happened in that meeting.
As for him coming back, I've said my piece on that. I hope he does. I think he will. And if/when he does, I'll enjoy his return and whatever he does as a member of WWE (I'm something of a fan of his, if you hadn't heard). If he never returns and I, SCSA, Heyman, Foley, and hundreds of others who've commented on it are all wrong, then it is what it is: he's retired, and I wish him the best of luck in all of his future endeavors.
wk
P.S.: Since I'm writing this 45 minutes before Raw, watch him come back tonight.