I'm really happy we're seeing a completed 364. Rekindling the excitement of a new release just like nothing has changed is a surreal ray of light in what has been a long stretch of darkness these past few months.
I figured we'd eventually see a rough version of it—whatever Miura had completed—added to the end of Volume 41. That would have been fine, but it seems we're getting much more than that. A posthumous episode with what could be Miura's final work.
It's natural to expect more after getting such a surprising gift, like a kid looking intently beneath the tree at the end of Christmas morning. Against my better judgment, that this is likely the end, I'd tell that kid: Well, we don't know precisely how far in advance Miura worked. Perhaps 364 was the last episode that was in a solid enough form that it could be released, but drafts or sketches of any future episodes Miura had begun will eventually see the light of day. That'd be a lot, even without the associated dialogue (like the portion of ep 348 we saw in the guidebook.) But I think hoping for more than that is a recipe for disappointment.
As for a continuation, I don't ever expect that speculation to cease. It'll just slow down along with momentum over the years. No explanation of how improbable such a thing is will ever be as palatable as the hope for what could be. And I have no argument that can beat hope.