Yea I remember him saying that too but It could be wrongly translated maybe ? or by switching with Obito he could have meant taking the place as Jinchuuriki of the Jyuubi and as the one to begin the Infinite Tsukuyomi instead of literally switching bodies with him (though I could be wrong since I don't remember the exact panels and context where Madara said he wanted to 'switch' with Obito so there may have been something that alluded to him literally switching bodies). I hope that we'll get to see for sure in the next chapter! Kishi really left everybody on a bit of a cliff hanger!