Lets hope Rockstar, as intellectual and witty as they are - despite how big they've grown, will not make a mistake as stupid as focusing more on online than single player....
It wouldn't be a mistake. It would be the smart and sensible thing to do, both from a financial perspective and from a development one. To ignore online play would be to ignore the future of the industry, which is financial suicide.
Just because a game is online doesn't mean there can't be a significant single player element. But taking resources away from what could be an incredible online experience to focus on SP is the wrong move.
SP and computer AI can never match the unpredictable and ever-changing nature of an online world.