In ordinary usuage, "forfeit" means to relinquish your rights, as in: "I choose to forfeit my rights to the property that I own".
Yes your sentence is correct
"He would have to forfeit his turn to answer the telephone."
"The man had to forfeit because he knew that there was no way he could win."
After suffering many casualties, the commander had to forfeit the battle.
The practice of plagiarism should mean the forfeit of marks.
The football team had to forfeit the game because they did not have enough players. She had to forfeit her car because she could not make the payments.
The team had to forfeit the game, which meant they lost, because they did not have enough players.
The African Luhya translation of the English word 'forfeit' is "Lekhana".
"Forfeit"
The soccer team had to forfeit the game because their players kept yelling at the referees. When he was convicted, he had to forfeit all of his illegal earnings.
Your question is itself a sentence which uses the word "could".
Old French.