*Picture from the /r/FFXIV discord via Miuna*
As reported by producer and director Yoshi P, there will not be an Ultimate in 7.3. There will be a next one in the series, however no news on when that would be. The most likely assumption would be 7.5.
That being said, MogTalk will still be working to do events for other pieces of content. Currently the new Deep Dungeon is being eyed for a World First event. Stay tuned!