Aside from getting people hooked, loot boxes tend to feed into a larger aspect of a kind of collection game. I don't see that stopping, and it'll likely continue to be a cheap way to keep people engaged in whatever platform is available.
Instead of a loot box, I'd expect to see more stuff like EA's Apex Battlepass or Blizzard's War Chest in Starcraft 2.
PS: I would happily throw money at any reasonable attempt to expand on Half-Life or Portal. C'mon Valve!