And the best is yet to come.
In the above sentence, to be to means "will", yet means "already". So, does the sentence mean the best has already come or that it will come?
"Yet" means "up to and including now", even when it's used with "to be to [verb]". So the best has been coming for a while, and it continues to come, but has not arrived yet.
Another construction with the same meaning is "to have yet to [verb]":