Obito may have completely absorbed the Zetsu suit. At least half of Obito's body is a Zetsu at this point, so absorbing the Zetsu Suit and beefing up is not so outlandish.
If Obito does keep the Suit, then this could help explain the rest of the questions about how Obito changes into Tobi. Assuming that the suit has Uchiha Madara's Mental Energies and some of his knowledge, it would easily explain how Tobi could claim to be Madara and how he would know so much information that only Madara should know.
Guess I am slowly becoming a CONVERT to Obito=Tobi = For real, and not incredulous.
(I still feel like Kishi has violated the memory of the only known good hearted Uchiha (not counting Shisui). I wonder if there is any of the Good, decent kid still left inside Tobi)