Daario Naharis showed up in Season 3 of Game of Thrones and he's been around ever since, though the character has gone through quite a few, uh, physical changes. Some might say that he looked like a totally different person when the show started up again in Season 4. Daario proved himself a helpful and useful ally at times, and he quickly won over Daenerys Targaryen once he joined her team. They became lovers and Daario was never far from her side after that. So where is Daario in Game of Thrones Season 7?
For an answer, one must only look to the finale of Season 6. Upon preparing to leave for Westeros, Daenerys realized (with some help from Tyrion) that she needed to cut Daario loose. She would have to arrive in Westeros a single woman, particularly because she might need to marry someone to cement her rule and having a side piece on hand would not be a good look. Though Daario wanted to come with her, Dany said her goodbyes and left Daario to look after Meereen in her stead. It's basically the equivalent of dropping your high school boyfriend before college starts. It's sad, but it's time to move on. But does that mean Daario won't be back for Season 7? That part is less clear.
In an interview with Entertainment Tonight, actor Michiel Huisman was questioned about Daario's future on the show. When asked whether he knew if a return was imminent, Huisman said, "Yes, I do, and I'm not supposed to spoil that." While it may seem like Huisman is dropping a major spoiler that Daario will be back, what he said is actually kind of misleading. He's only saying that he knows if the return is happening — which could mean he knows it is happening, or knows it is not.
But whether or not Daario makes an appearance in Season 7, Huisman seemed glad to get as much time on the show as he did, especially since his character didn't meet his demise at the end. "Being part of Game of Thrones, you're always expecting your character to die," he said. "You're not mentally preparing yourself for a very long haul."
It's not certain yet if Daario will show his face in Season 7 (perhaps just to provide a little update on how Meereen is doing without Dany and her dragons there), but if he doesn't, then at least his arc didn't end in bloodshed.