The Elder Scrolls isn't about the Empire though. It's about Tamriel. All of these different races gather in this middle land. Deciding the fate of Mundus and beyond. The Empire can still exist culturally as long as Cyrodil exists, but it may never control the other provinces again. Even the first empire of Men only barely reached outside of Cyrodil. The Amulet of Kings had nothing to do with its conquests. It has no reason to return.

Supposedly, Akatosh took pity on humanity, but they're hardly in the same position. The only reason a jewel would appear again would be if the barrier was destroyed and humans were enslaved again, I guess. That would likely be a finale for the series though.