Well, we find out how Obito got the long hair. Also, I figure since he wears the "Hashirama" body, the cells made him grow faster. Everyone should know by now that Hashirama cells are the answer to everything. Any thoughts? XD
Yeah I think Zetsu acts as a cocoon, which would explain on the last page bottom right we see Obito reacting to the growth. I don't realy know though, just guessing. XD