OK, so I get that this looks like it's in no way related to the Ultimate Universe, and I think we're all working from the premise that the UU is dead, and that 616 will eventually return in some form.
Yet, some aspects of Battleworld are obviously going to be sticking around. Hmm.
And then, today I saw the tagline for the relaunch of Amazing Spider-Man, apparently still a thing after all: "Your friendly neighborhood just got bigger." Double-hmm.
I've now got half a hope growing in the back of my mind that we might actually close very few doors with the end of the Ultimate Universe, rather than all but a very few (Miles, and... well, that's all we know of for now): what if the multiverse doesn't actually end, but instead becomes permanently collapsed in some manner that allows characters to move freely between worlds, indefinitely?
In the original Secret Wars, basically everything is destroyed as well, and then it all gets rebuilt. I'm not sure how often Eternity, Infinity, Chronos and the Living Tribunal show up these days, but for awhile the Marvel Universe was getting collapsed and destroyed and rebuilt with some frequency. Which means, basically anything can happen, no matter what the billing's been.
And I think a collapsed multiverse would be a pretty interesting and workable, and maybe stable, concept to work with. It also fits the way that our lives and stories and communities and environments weave together on many planes in our modern, networked society. A single world with many layers. It provides a nice status quo, but also maintains a tension that could be resolved later by re-disconnecting the multiverse, or what have you...
I awno I'm just thinking out loud here