Wally didn't go back to being Kid Flash because he's an adult.
Guy Gardner became Warrior, John Stewart became a Darkstar, Kyle became Ion, and Dick Grayson went back to Nightwing, Bart Allen went back to Impulse, etc.
By the nature of comics being an endless loop, Red X being someone who's an established hero would just make them going back to that previous mantle inevitable.
Anyways, is your theoretical Red X confirmed to be in the Teen Titans Academy book?