What do you think will happen? Does Sasuke finish him off or leave him there like Itachi more or less intended, so that maybe Izanami will work and he'll change his ways. Think he'll come out of it then release Yamato and Anko? (for good deed reasons more than combat tactics since Edo Tensei is over and White Zetsu army is pretty much gimp now).

Or do you think Kabuto will stay, have his change of heart, and be found by his brother who we know is fighting in this war from that little scene back during the Kabuto fight sequence?

I'd like to see him change his ways. Sure, he's a mega criminal, but there's the variable of that scroll Suigetsu found. Maybe it'll take Kabuto's help to make it work, but that'd depend on how much the scroll is actually required, and what it does. Only way Edo Madara can be defeated is A) someone forces him to release the seals on himself via genjutsu, and that only person is Sasuke, but we're not sure if they'll meet yet even though it seems like a probability from our external POV. B) Someone seals him; who can do that? Gaara has seals but thus far they've failed, though they've failed mainly cause he hasn't been able to lock one in. I just doubt at this point Madara can be overpowered by a seal, so perhaps that scroll relates to Edo Tensei, and perhaps Kabuto changes his ways and helps out there?

Plus, White Zetsu supposedly got his spores on Kabuto. That could either be a plot hole, or just Tobi's way of keeping track of him, or it could serve a more surprising purpose if Tobi wants to take control of Kabuto for some reason.

What do you think will happen with Kabuto now that Edo Tensei has more or less been defeated, but at the same time made more of a threat considering what Madara just did?

I think he'll leave him there.

1. Kabuto will probably stay there until he changes his ways.
2. Seals don't last forever, when the user dies, the seal goes away. Meaning that if Gaara were to seal Madara, when Gaara dies in 60 years, the seal will vanish.

Madara is unstoppable, no matter how you put it, UNLESS he is forced to cancel the jutsu, for that is the ONLY way that this will end.

Are you sure that seal vanishes after the caster dies?
Hiruzen sealed Oro's hands and they didn't come back after Hiruzen died.

Death Reaper is a living entity, Hiruzen summoned the Death Reaper. The Death Reaper (someone who never dies) does the sealing.

Basically, making it the ultimate seal. The only thing that makes it a bad seal, is that it consumes the summoner's lifeforce.

It's not REALLY a summoning jutsu, but you summon the spirit, the spirit does the sealing.