Sasuke could decide the end of the war.

[To Whatever]

Naruto could have decided the end of the war as well...

and Obito

and Madara

and Kabuto

and Itachi.......

 

[D R E X]

Your logic is pretty flawed for a few reasons.

< Assuming Sasuke does join Madara it would be for his own reasons. Madara only insisted on killing Obito because he was in way of his goals if Sasuke is cooperating then he would use him/ kages against the enemy.

< If Sasuke is there BZ would have no opening against Sasuke/Madara until IT activates but by then there will no enemies so all of Madaras focus would be on BZ.

Okay, the second I can agree with but the first still bothers me. I'm just mentioning the possibility of it:

*Madara was gonna take Obito's life anyway due to his revival process, not only because he betrayed him.

* Madara wants to operate IT without any interference , and knowing Sasuke could pose a huge threat by his side, he'd defiantly want Sasuke dead, because there are a lot of chances that Sasuke would end up doing so, personality wise & on the main intention of Erasing everything of the past.

It's hard to predict on where he ends up leading it.​