You may recall that Alvarez had been one of the names rumored to direct Doctor Strange, and while he doesn't confirm that exactly, he does tell ScreenCrush that he and Marvel did enter negotiations, but that he decided his energies were best spent elsewhere...
“A lot of those movies are cool and audiences are going and watching them. It’s just as a director it’s harder to have your vision in those, if you go and do a Marvel movie… At some point we were in conversations and… they already figured it out. They’ve figured out the style. They’ve figured out the way they shoot them. They’ve figured out the colors, the humor. What would I do? I enjoy a lot more freedom than that. I don’t know. Eventually I might . And it depends on probably the characters in the stories. But just something about my job as a director that I really enjoy is creating my own thing.”
So he's still open to the idea, and maybe if/when Doctor Strange gets a sequel he'll be on Marvel's speed dial. Although personally I think he'd be a better choice for something like Blade. Alvarez's next film, the horror Don't Breathe, opens August 26th.