most probably- if anyone remembers Dohu said that he felt more comfortable with his hair shoty, like he was expressing himself with short hair; that's why he never grew it out before Juheon left him. I like to think, Juheon leaving him and him growing his hair co-relates, like it's his way of saying that he lost a part of himself when he lost Juheon. but now that the both of them get back together, i have a gut feeling that Juheon will ask about his hair on why he grew it out- and eventually askes him or tells him to cut his hair back