Faith will not be needed (or possible) in the Millennial Kingdom, since the Law will be clearly defined, there will be no Satan as temptor.
Faith deals with the unseen not the seen.
The Millennial Kingdom is a return to the conditions of the Garden, where obedience not faith was the issue.
With the Millennial Kingdom God's Plan comes full circle.
OK, ftD, I'll concede this one to you. I'm thinking of "trust" perhaps. My only caveat is Jesus' words to Thomas, "blessed are those who see and believe...more blessed those who do not see and yet believe."
But Hebrews says, "faith is....evidence of things Unseen."
Perhaps these tie together in the word "trust." In any case, you are correct that obedience will be a critical issue.