Here is the most crazy idea my brain has make-believed-
Titan was scrapped a few years back due to the changing dynamics of the MMO marketplace, and Blizzard wants to continue to support WoW for the next 10 years. Wouldn't be too hard to believe. Titan WAS supposedly shelved/re-started because it had no place, didn't "fit" in the world anymore.
Project Titan shifted to become a new, "next-gen" engine for WoW. Sure, they've made lots of additions and changes to the engine since launch, but the base engine for WoW is running on 13-14 year old code.
New Titan engine for WoW - just as scalable, works on 300$ best buy laptop with integrated gfx up to many thousands$$ gaming PC with all the bells and whistles. Maintains vast open world - traverse whole continents without loading screens. Much improved animations and overall graphical fidelity (including new racial models for all vanilla/tbc races.) More dynamic water, weather, terrain, flight models, underwater movement, etc. etc. And the big kicker - vastly improved scale. Easily handles tons more players on screen, more massive fights, bigger battlegrounds and raid environments, including city sieges on a massive scale, larger more epic bosses (Deathwing "riding on his back" less of a gimmick, more "Shadows of Colossus" etc.)
Kind of a 10-year reboot of WoW for the next 10 years, and give purpose to the work done on Titan - Project Titan, WoW for the next decade.