So again another Future Barry Theory.
So maybe in the next episode, Barry tells Emo-Barry his plan on how to save Iris from Savitar and Emo-Barry becomes frustrated that Barry is STILL messing with the timeline even after all the destruction he has caused because of time travel, to stop his past self Barry finds the Philosopher's Stone and becomes Savitar and fights with his younger self to maintain the timeline and prevent the Black Flash from taking him into the Speed Force as Emo-Barry would become a Time Remenant. Barry fights with his future self to save Iris's life and Emo-Barry is only trying to protect himself and the timeline from Present-Barry's selfish choices.
My earlier theory on how they could save Iris could also be done with any other member of Team Flash.
I do have strong reasons as to why Future Barry is Savitar:
1. He says I am the Future Flash.
2. He said to Barry "From my perspective, your the big bad".
3. He knows everything about Barry's life.
4. Jay Garrick said that Savitar was the original speedster and Barry was the first Speedster.
6. He said to Barry "Only 1 of us could live" this is because Barry is trying to change the future and erase Emo-Barry.
7. He claims to be Barry's greatest enemy and who else could torment Barry more than himself.
8. He says "He didn't ask for any of this" which implies he is tormenting Barry targeting Iris out of pure neccessity.
9. In Episode 15 He told Barry that they will meet soon and Barry is just about to meet his future self and Barry is there when Savitar becomes who he is.
10. He apologises for "Having to Kill Iris", this makes it seem a lot like Barry.
11. He knows that Barry is trying to change the future, this implies he is at least a member of Team Flash.
tl;dr - This is basically a summary of the clues as to why Savitar could be future Barry and what his motivations may be.