Cisco refers to Savitar as "Two-Face" after he was rescued by Gypsy. This is a tongue-in-cheek reference to the comics villain Harvey Dent, aka Two-Face, an antagonist of Batman who also has the left half his face severely scarred.
The story that Barry talked to Savitar about could be a reference to the beginning of the animated DC movie "Justice League: Flashpoint Paradox". This storyline was also the catalyst for Season 3.
The scene where Savitar holds Cisco while vibrating his hand and telling him that he will die "the same way twice" refers to his death in the erased timeline in Out of Time.
Savitar is killed the same way that The Rival was killed in Flashpoint. The Rival was shot in the back by Joe as he was trying to attack Barry from behind, and Savitar was shot by Iris when he was trying to do the same to Barry.
In the final scene, Iris calls Barry "Wally".
In the previous episode, H.R.'s last word to Cisco is "Till next time" and salutes him after he puts on his hat.
However, in this episode the flashback shows it was changed to "Till the next one" and H.R. slightly tips his hat.