Avengers: Infinity War - 10 Possibilities For The Secret New Character
7. Namor

After some confusion over the rights for Namor, it seems Marvel do have them back and could make a Submariner movie if they so wish. Given how heartily fans have called for that since the formation of the MCU (and that early tease in Iron Man 2 that he was a background figure in the universe), it's got to be inevitable that it'll happen at some point.
One rumour - courtesy of Reel News Hawaii - suggested that Marvel might actually be making a secret Namor movie already, which is rather unlikely, but it doesn't change the appeal.
Considering the global scale of Thanos' attack - universal would probably be a more fitting term - you'd think that Atlantis might send a delegate to find out exactly how the potentially genocide-scale events are being dealt with. And if that then set up the formation of a version of The Illuminati, we'd definitely have a fan-baiting moment.