Season 3 spoilers ahead
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After I finished watching the second season, I strongly believed he would not return, and that was the end for the character, but the promo for upcoming episodes of Season 3 hints at the possibility that he could be pretending to be one of the other hosts. (He would have been in one of the cores Dolores took out of Westworld.)
With it being a promo, it could still be false or there could be some misdirection - but if Teddy really is still on the show, I really like the idea that he could be passing as Charlotte Hale, or the new host played by Tommy Flanagan in the S3 premiere. It feels like a very Altered Carbon way of bringing back characters, and it works even if there is a version of him in the Valley Beyond.