I think you have to determine what is better for you:

If you wait until next season, your players lose a * and $$$ value, BUT at the start of the season, auctions are hot and you might get a great $$$ from the managers lower than you.

Otherwise, you sell now and hope you get the panic buyers who want to move up the table or win the cup final.

I would suggest selling now while they dont lose a * and $$$ value.