When a team goes 7 economic updates without logging in, they become. a bot. That won't really change anything, other than the team then being available if a new person signs up for BB. If he still had players on his roster, those above a certain salary would be sold off; similar to what has already occurred here due to bankruptcy. I don't think any new players are added though, so the team will be continuing to forfeit.
Assuming a new player doesn't join and replace him, during the off-season, all bot teams demote, regardless of where they finished, and a new team is promoted from the lower division to take their place. So rather than getting the normal 4 promotees from D.V, you'd have 5.
Having them finish the season forfeiting is perhaps the fairest approach. They began forfeiting right at the start of the final third of the season, so played everyone once and then all of the teams in their conference will be getting a forfeit the second time they face them. Rarely does it work out quite so nicely.