This series just got 400% more cliched!
*chuckles* Well, strictly speaking, any cliche inherent in that turn of events I counted as applying way back when Jiraiya said the same thing as he was dying...
Why the heck would Madara steal a crippled, dying kid's body if he wanted to use Orochimaru's immortality jutsu? There were still plenty of other Uchiha's around at the time, if he had to have a Sharingan. Not to mention that the immortality jutsu only lasts for 3 years, and then the user must steal another body. Obito died what, 10-15 years ago? Unless Madara has improved the jutsu or invented his own superior version, he wouldn't still have Obito's body now even if he had stolen it.
The former I can't say, but I could easily imagine an as-of-yet unknown ulterior circumstances intervening to force the choice.
As for the latter, I always interpreted Orochimaru's degeneration to be a lingering, continuous effect of the Third Lord's curse. Is it ever stated that there's an inherent three-year limit to the jutsu?
Consider: Orochimaru had already performed the jutsu once before the start of the series. Given that there is
unquestionably a similar time limit before the jutsu
can be used again--and he was planning to take Sasuke's body right away, that means he should have been similarly incapacitated during part one, if there were an inherent time limit.
Regardless of whether that's true to not, at the very least we know that Madara is someone we already know, otherwise there'd be no reason to not show his face even after we know who he is.
Well,
strictly speaking, he could be someone we
will meet at some point between now and when his face is actually revealed.
But I agree with you, it probably is someone we've seen already. And yes, Obito is certainly the front-runner at this point.
(And, if
that's the case, it's probably also a no-brainer who's going to have to take on Madara in the end.)
Finally, why the hell is Sasuke accepting Madara's help?! Madara helped murder his freakin' family! He should be trying to kill Madara almost as desperately as he did Itachi!
Well, the fact that he changed his feeling over the death of his brother indicates that he has some degree of sympathy for why Itachi did what he did. Turn it around the other way--he shouldn't feel much
worse about Madara than he
currently does about his brother.
---
I also found it interesting in the previous chapter how Madara's snide comment about how Itachi's failsafes "only got as far as the 'fail' part" turned out to be, in fact, rather premature--as Sasuke wasn't the only one he gave part of his power to. Any bets on what he left for Naruto?
Myself, I'm guessing it'll take the form of some kind of genjutsu resistance, since A) that's Naruto's biggest gaping weak spot right now, B) Itachi had, himself, observed this in the Rescue Gaara arc, and most importantly C) it'll be a rather un-cinematic fight if the two of them have to do it all without ever looking each other in the eye.