They will probably go back up.
A lot of puppies ears go down when they're teething. Tate's actually went up, down, up, down several times before he finished teething. Now they're always up!
I've heard rubbing/massaging the ears can help train them to stand up, also.
__________________
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion. -- Author Unknown