The vast majority of big-name retailers just won’t stock an AO rated game. Worse, even if Rockstar wanted to go ahead and release the game, Nintendo and Sony won’t license AO games for release on their systems.
This really only leaves Rockstar with two courses of action: Cut the game to get an M rating, or fight to get the game re-rated leaving the content intact. Either way, with the game’s release date only three weeks away, it’s going to be a miracle if it doesn’t get delayed.
Fighting the ESRB may seem like the best option since that would save them having to edit the game, but given all the political pressure on the ESRB these days, it’s hard to imagine them budging on such an issue.