The Nolzur's Marvelous Miniatures Mystery Box features a full value box of surprise miniatures, waiting to be painted. This mystery box contains: Four 'single' pack unpainted minis Four 'double' pack unpainted minis Three 'tall' pack unpainted minis One Chimera (with included paint brushes)
shop.wizkids.com
Yes, loot boxes are unpossible in D&D!
Pointing out that Wizkids =/= WotC, but also that there are quite a few miniatures collectors who are just that: miniatures collectors, not D&D players. Though most are both, to some degree (or Pathfinder, Heroclix, etc.).
In fact, over on the Minisgallery forum, which I frequent, there is quite a notable divide between those, like me, who see miniatures as game aids, and those for whom collecting miniatures is the whole point.
Edit: to the larger point of whether "mystery boxes" of some sort could happen in D&D...sure. Why not? They wouldn't offer a competitive advantage - you can't really, in a game that is ultimately arbitrated independently at each table - but if people want to pay for a random assortment of stuff, whether analogue or virtual, that seems to me like that's their business. Dwarven Forge have offered a random sampler terrain pack for years, and they're not the Antichrist or something.
The larger issue seems to be whether the VTT will jack up prices on the game. I think it'll drastically lower them for the young Clints of the D&D world. I have spent a small fortune over many years on physical miniatures and terrain, and I will bet you anything you like that the prices for the VTT will be exponentially lower.
Will I switch? Ooooh, that would be painful. I love painting my stuff and building my sets, and like I stated, my sunk costs are hideous. But I'll try it out and if it is easy to use for a grognard like me, I'll probably wind up using the VTT when I'm not playing at home, just as I currently use the 2d map tool.