Pretty sure this will never happen. I don't think theymos wants the forum to be holding money for random people.
Plus we don't even have 2FA.
Mods don't want to do this cause it would make Bitcointalk a target for thieves looking to make a quick buck.
I had an idea about that, though I'm not sure whether I'll do it. The forum could accept BTC and in return give "forum credit", which could not ever be withdrawn for BTC, but which could be used for ads and donations. Since forum credit has value, a market would develop with an exchange rate somewhat less than 1 BTC per BTC of forum credit. A micropayment system could be based on forum credit; receiving 1 BTC of forum credit would be just a less convenient and more centralized way of receiving ~0.95 BTC.
Very interesting concept, but I had something much simpler (and less risky) in mind. User enters send/receive addresses in profile, and a button is displayed on every post (in the sig or sidebar or wherever) that allows anyone to micropay directly. The forum would not hold onto the BTC at all, just a direct payment. Or maybe you could skim off 1%, etc. You might need to ratchet up your servers' security a bit to prevent hackers from changing peoples' profile addresses, but it's a pretty simple plugin I'd imagine.