Portal multiplayer is already a thing so it is technically feasible. There is also Wraith from Apex Legends which spawns portals as well, but you cannot look through them. Source 2 is also definitely capable of making it happen, so honestly most things point to the fact that yes, they can have a hero like that.
However, it would probably be more limited compared to how Portal works. I expect that all the physics/momentum conversion mechanics to be impossible or really not worth the effort to do. There is also the question of how it would influence the map and so on. If they didn't plan a hero like that from the start and didn't make the game to work with them from the ground up, then i doubt it will ever happen.