We have seen that when Flash had an amnesia, Wally lost his powers. But when Savitar died, that means he was never created in the future, and hewill never plan on creating Wally as a speedster to take his place in Speed Force. That means Wally shouldn't be a speedster, right?
The Flash messed up its time travel logic in season 3. In episode 21 of S03 "Cause and Effect", for plot purposes, Savitar loses his memories and therefore events lead to Wally not getting his powers. Ok.
So, then using the same logic, Wally currently shouldn't have his powers, right? How is he a speedster now?
Season 2 had already given the answer.
While in S02 episode 11 "The Reverse Flash Returns", it is clearly explained by Harry that Nora Allen's death is a fixed point in the timeline, and stopping the timeline remnant Thawne would not change what happened in the past. Granted, the future is in a constant state of flux, but the past would remain unchanged iff a time traveler does not tamper with the said time in the past.
I don't know why this is such a thing now - using the same logic, in S01, Thawne getting erased, should have resulted in Barry losing his powers, since Thawne would never create the Flash, and Barry's mom should have walked from the grave, as Thawne would never kill Nora Allen.
The final solution is -
A speedster getting erased from existence at a certain point in time does not affect his actions that had taken place in history. The savitar that gave Wally his powers has become a time remnant, as in he was already a time remnant, but now he is a time remnant of the Savitar timeline, where he exists to solely to serve his purpose to the timeline, so that paradoxes do not occur. The speed force preserves such timeline remnants, to prevent further paradoxes that would impact a certain timeline.
I have a really clean and simple solution if you've gotten tired and confused due to the answer that I gave and have scrolled down
- FORGET SEASON 3 EVER HAPPENED.