With over two million copies sold, I think it's fair to say that PlayerUnknown's Battlegrounds is doing alright, money-wise. The developers hopefully will not starve. They do, however, have plans to make more money off the game in the future. But not until it's "done".
In an interview with Gamasutra, Brendan "PlayerUnknown" Greene said that PUBG will eventually get loot crates that you can use keys on to unlock cosmetic upgrades, a la games like CSGO, with the ultimate goal of creating "a valuable economy".
"We're not doing monetization during early access," he said. "It'll be afterwards. So we'll have keys to open crates to make it simple. But we'll also try to have rarity, so by opening a crate you can get a skin that's worth £10 or $20."
He added, however, that he's strictly against gambling, so probably don't expect the Bad King of "valuable" economy to spring up.
While players generally dislike it when developers start charging for skins and things of the like before games leave early access, the battle royale genre has an especially fraught history on that side of things. Genre kingpin H1Z1: King of the Kill has been dinged repeatedly for its forays into monetisation despite persistent bugs and a general lack of polish. That in mind, Greene and co's decision to hold off for now seems like a pretty smart idea.