You're not destined to get worse, but there's no way for anyone to predict what it will do. Might get better. Who knows?
There's no reason to think that the afib will prevent your surgery from happening no matter what it does. Afib is rarely a show stopper for surgery; the surgeon just needs to know in advance that you have afib. So your cardiologist and your surgeon need to be talking well before the procedure date. Make sure they're communicating and you'll be fine.