They said the other Ultimate is currently in the works. Given there is probably a year and a half until the next expansion, it would be odd for it to take longer than that.

I think the reason the other one got delayed was because of Covid and the delayed assets and challenging conditions they had back then, combined with them being busy with MSQ development. Since then, they've been hiring battle designers like crazy as well, and are even hiring them right now.

I think the reason they usually don't do it after 7.3 is because that's when the development of the next expansion actually begins. They start making all the leveling dungeons, zones, models, and so on, so their team can be too stretched to focus on that. But with the increased amount of time for an expansion, people being used to covid now, and the increased battle designers, hopefully it won't take that long this time.