Ultimately they will struggle for a few years, until they straighten themselves out. They need a new owner for starters, probably manager too, although Moyes is good enough to take them back up.
Then they need to clear the deck and desperately keep a hold of any younger players/experienced pros in their squad.
Defoe won't stay.
Give it a few years and they will be back. Although they are small time to us, they have higher expectations than most in that division.