Don't check in until you have a seat you like, or rather don't print or App the boarding pass. Check every few hours since that suggests an oversold flight and they will have to do something, like move the curtain or find a spare A321. Just check every 2 hours or so, you will hopefully see some movement. Usually seating changes rapidly in the first hour after OLCI. So play the long game, I'd give you a high chance of success.