"One will betray you" - My bet is on Wally. Caitlin would be too obvious, Cisco would be redundant. But I can see Wally feeling abandoned and not trusted, and turning to someone who seems to care for him, but will end up being the worst possible guy ever... (see my point 3). Plus there is a strange camera move. When Julian said the line, the camera moved directly to Wally... That being said, I doubt the betrayal will be permanent and the betrayer will return to the "good side".
"One will fall" - Probably Iris, but there is of course more to the scene of her future death. Maybe Julian will end up sacrificed himself to redeem himself for his new friends.
"One will suffer a fate worst than death" - the third point. Many seems to believe that it's the least important point, I have the feeling that it's the most important one. "A fate worst than death" doesn't mean for me suffering the death of someone, it's the most terrible fate, when you are, for exemple, prisoner of your own body without being able to move or speak to anyone... or being trapped "in eternity" without an actual physical body, for exemple. You know what I mean ? I've the feeling that this line is a way for Savitar to say that someone in the team will become him in the future, someone that will be trapped by future Barry and then "suffers a fate worst than death"
Now, If we analyze who it could be. What if the mid season finale was the true demise of Savitar, and we will now see his rise until he is trapped by Barry ? Savitar is a product of the post flashpoint timeline. Who may not have been in the team or have changed drastically between the two ? Savitar said that "You're a God if you make people believe that you are one", something that a conman can say. And if Wally ends up being the betrayer, who may he trust more than the rest of the team ? a friend, some kind of mentor ? Now there is a possibility of Savitar being a future and corrupted version of Wally, but many, many clues point to HR, so I will bet that HR is Savitar and "the one that suffers a fate worst than death"