Hmm, didn't Daenerys make a similar oath of vengeance against Jhaqo in the show that she did in the books? I seem to recall when Rakharo's horse came back with his severed head in a bag, and Jorah speculated that it was either Jhaqo or Pono, Daenerys made some sort of oath of vengeance against his killers to comfort Irri.
I was thinking they might not even have Daenerys fly off in the TV show, but if they kept that oath in, it seems likely that they're also going to have her end up confronting the subject of the oath.