I think he will be rescued by Capt. Marvel at the end of her movie. They both then will hook up with Tony Stark to figure out how and where everyone disappeared to.
This is what I'm thinking also...
- Gomara (daughter of Thanos) might still be alive
- on IMDB next Avengers movie ( part 2 to Infinity Wars) - list Evangeline Lilly (the Wasp) as part of the cast (though she was "dust")
May 2019 can't come soon enough