The 8th umbral calamity

[AwesomeJr44]

As for time travel itself, I too believe they'll likely bury that hatchet post-Pandaemonium. It's a consistently convoluted plot point that they see no further need for at this time.

I certainly hope they do. Time travel is a very difficult thing to write well, and Endwalker has proven that the writers can't use it properly.