At this point, Savitar Being Barry is more probable than Savitar being Wally, for a lot of reasons :
1) Savitar seems to be a master planner and a great strategist, and I don't think that it really fit the impulsive and more spontaneous personnality of Wally. Yes, if he was trapped in the speed force for centuries, he can change... but I think that even before his transformation, Savitar was already a strategist.
2) I don't think he could kill his sister, especially after how he reacted at the vision of Iris death
3) Savitar said that that Barry trapped him in the speedforce, but it's Savitar who trapped Wally
On the other hand, I'm more and more suspicious of HR, whose personnality fits way more the one of Savitar. He seems too cool and confident in his discussion with Savitar, plus isn't he the one who pushed Cisco into making Wally see Iris death, ruining Barry bad plan with the ring.
He is the one who call Wally "Wallace"... like Savitar. He is the one who is the con artist, exactly the guy who would persuade other people that he is a god. Plus, Abra Kadabra, who is supposed to know the true identity of Savitar... is from Earth 19, if I believe the synopsis of his episode, and who is also from Earth 19 ?
Yes, he is supposed to be present at the same time as Savitar in the vision of Iris death, but Savitar is a speedster, and we all know what the speedsters call "speed mirages"