Of course his fans will regret his decision a lot, but if it's a good decision for him everyone has to respect him regardless of the issue with Deschamps which is currently being discussed, I will of course support whatever decision is best for Benzema, he is the best player and he seems to be maybe he wants to focus on playing in the league with real madrid until he retires completely from the world of football
I don't know how bad the situation is at the moment, but to be honest I'm more worried about his condition at Real Madrid this season. I think Benzema will have to stay strong to have a great season even though he has been suffering from injuries for a while. It is expected that his recovery will be faster and he can contribute to Real Madrid better.
There are lots of rumors about a new striker who will replace him as a starter, but I hope Real Madrid will handle it well. Benzema is the best in his position at the moment, but I admit he has shifted a bit this season.