What happens when a player who has quit is not joining a tournament game? Is the tournament going to be stuck there permanently?

Tournaments, once they've started, make people join automatically unless they have a colour-conflict with another player. After three days they are forced to join. Then they can get booted in the game in peace.

not necessarily three days; they're forced to join after the boottime, so if the boottime of a tournament is 10 days they have another 10 days to pick color which can slow things way down.

But it does indeed autopick a color, a tournament can never get stuck permanently unless it's bugged out in which case you should report it to fizzer.

Ok, I think it might just be the boot timer because this match: https://www.warzone.com/MultiPlayer?GameID=17950657&From=MPDashboard

has taken a long time, but after looking back it has not been 30 days yet. Thanks.

Ah right. Guess i'm too used to the 3-day boot timer :p