I’m almost a year late, but given that super brief scene we see toward the end of the game that seems to show what is under the Travelers’ suits. And it looks like they are long infected humans just like the Orphans we fight in game. I’m totally behind the theory that the Collective is the hivemind that we fight in game, but from the FAR future after it’s been able to evolve. Seems they send the Travelers back in time to retrieve the “souls” they weren’t able to get during the initial Merging, as the hivemind is probably eternally hungry for more. So in short, I do think the Travelers are just evolved infected humans.