The idea that Barry becomes evil in the far future and is trying to kill his younger self, just does not feel right.
Savitar isn't trying to kill Barry though, at least not yet...
I agree that all those "I'm the future Flash" repeated over and over can't be a coincidence, but it might just be a red herring. Because
which Flash, that's the question... Barry seems like an obvious choice, with Savitar trying to kill Iris and destroying all that matters to Barry so that he would turn evil and become Savitar, but that just seems too simple for the usual speedforce shenanigans. Wally, on the other hand seems too complicated because then he's trapped himself in the speedforce and that's slightly too wibbly wobbly...
So my theory... I'd say it's been Julian all along, or more accurately he's
about to be.
Savitar says he created himself, which would fit because all this began when he found the stone, Julian has a thing for mythology, he now knows the inside details of the team, and both Savitar and Julian have similarly smug and self-important attitudes... Also, it just could be that the Julian as Alchemy thing was made
so obvious precisely so that this would come as more of a surprise.