Let me start off by saying just because the chap is named ‘Uchiha Obito’ and Kakashi asks at the end if it’s Obito, doesn’t mean it’s him. Kakashi is asking if it’s him, and the whole chap are flashbacks about Obito, therefore that’s why the chap is named Obito.
The only reason I can see Kishi trying to bullshit us in making it Obito (although there are way too many plotholes) is to add more significance to Sasuke and Naruto’s upcoming battle. Naruto will see what Madara or Oro did to a Uchiha (Obito), and think of Sasuke. Naruto will also see Kakashi’s will to kill his bestfriend, Obito, to protect his comrades. This will play an important role in the series, because Naruto will soon have to do the same. Kakashi will probably die in this heroic attempt enraging Naruto to come to a realization that his handful of current friends are worth more than an emo, egotisitical, bastard, bestfriend, Sasuke.
Since it is completely illogical for it to actually be Obito, I’m going to wait for Kishi’s explanation. I pray that the Izuna + Zetsu + Obito all in one vessel theory is true, because we all know Madara’s brother has to be a badass. On a another note, I wonder what Izuna’s Susano’o looked like. *scratches head* Probably cooler than Sasuke’s
To sum it all up, if it is Obito, whatever (his debut was awesome). If it’s Kagami, Izuna, Madara’s son, or the elder son of the So6p, even better. I just want my explanation.
It's not completely impossible for it to be obito, while I do agree with a lot of what you said though. This is the world of Naruto, anything is possible at this point.
For all we know Hidan is going to show back up unscratched.