Or they could just take back a cap dump. No way in the universe Buffalo should retain anything.
Which most likely is the way it would happen.
But that would rule out a team like the Avs who don't really have capdumps like that (especially not guys that don't have the ability to block a trade to Buffalo).
I also think other teams like Vegas would maybe not insist on retention (like the Avs) but atleast significantly increase their offers if they retain.
The most interesting speculation on that came from Friedman who said that the league might be willing to do a one-off and bend the rules a bit to get out of this mess that nobody (Eichel, Sabres, NHL, NHLPA) is happy with right now.
For example my sugggestion would be to allow the Sabres to retain 2M/ year but have it (the whole 10m) fully count against their cap in 2021 / 22 (where it really wouldn't matter capwise for them) and then don't charge them any further for the retention in the following years.