: To my understanding, the Flood nearly accomplishes total extinction of the
: Forerunners after the godly annihilation of the Greater Ark, I guess it
: can be called the Battle of the Greater Ark, with use of whatever the
: 'Star Roads' actually are.

Is that what led from Earth to the Ark?

: Forerunners are said to live long but I doubt 100,000 years long. That's just
: the fate I believe Iso-Didact would be left with, but factually we are
: left with 2 Forerunners whose destinies are yet unspoken for.

The Didact (or one of him) was alive though; I'm guessing the cryptum is what makes that possible. If the other one went into a cryptum too, he could still be alive, unless there's another twist they want to throw at us about how all this works. I think you're right about him probably making absolutely sure the reseeding goes off without a hitch, but once that's done, he could enter a cryptum-- going by Halo 4, he probably could've watched it all from inside a cryptum.

: Now that I pretty much covered the bare facts as the trilogy came to an end,
: the only Forerunners we are left with are Ur-Didact(who we faced and
: defeated so his fate is in stone),

not so fast, a lot of people are theorizing he's still alive, at least to some degree, and the sample of the Halo 4 visual guide that was put out recently says that he might still be alive (specifically this); I don't think they'd do that if they didn't want to bring him back or at least have that as a plausible threat (one we might have to stop by shooting things)

: Anyone else have theories on what they personally think happened/happens with
: these two remaining 'gods'?

I don't know, but I think if the other Didact or the original Librarian, or possibly any form of her, is/are still alive, it would be the final undercut to the Halo 3 terminals-- not to their canonicity necessarily, but it would undercut the impact they have in light of the rest of the canon Haloverse, and that would be a shame, because they tell a good story.