As of 2 hours ago, he is said to have offered it.
According to Jon Western:
This can not end well for McChrystal. He has a lot of support here, but this crossed so many lines– civil-military relations, leadership judgment, command authority, the raunchiness of his conduct, etc… Given the complexity of the on-gong operations and the multiple levels of coordination across so many different civilian and military organizations operating in Afghanistan, there is no way McChrystal can credibly command ISAF. No one will want him commanding their forces. And, given the wide swath of his attack — directed against the entire civilian and political leadership in Washington working on Afghanistan — he can’t possibly continue to work with them.
Maybe true. If Obama accepts his resignation, it may send a strong and worthwhile signal in terms of civil-military relations. But it will also remove a commander who has done more to protect civilians in Afghanistan than anyone since 2001. Afghans understand this. Michael O’Hanlon has more. Also see Joe Klein.