They're milking this "Who is Savitar?" thing for all it's worth.
At this point I honestly don't know. First thought after the ending would be Ronnie, but him wanting to be rid of Caitlin is completely out of character. And before this episode I thought it was future Barry but that doesn't seem to be the case, unless future/emo Barry becomes Savitar sometime after 2024.
At this point my best guess is that Savitar is actually one of the time remnants that Barry uses to try to beat Savitar. Maybe the time remnant hates Barry for being the "real" Flash and feels like he wasted his opportunity to live out his life after Iris died. In any case I think Savitar's prophecy is confirmed -
One shall die - Iris
One shall betray you - Caitlin
One shall suffer a fate worse than death - Wally (being crippled and mute for the rest of his life)