lol well we know he didn't kill himself as he would eventually create the Leaf Village. And he wouldn't kill Tobirama as he would end up teaching Hiruzen and co.
So really it is obvious that Hashirama will simply heal Madara and let him live. However, this means Hashirama either lets Madara free, without gaining his trust back. Or he did something else, an alternative to option A and B. It has been debated over whether this alternative was Tobirama reviving Izuna with edo tensei.. however.. I guess we'll see soon enough.