Brendan "PlayerUnknown" Greene held a Reddit AMA today where, among other things, he revealed that mod support, while planned for the game, will not launch as part of the full release of PlayerUnknown's Battlegrounds.
In response to a question asking about a planned mod support for PUBG, Greene revealed that while mods are coming to PUBG, it will not be part of the full release launch-currently scheduled for later this year.
Greene previously talked about mod support in PUBG in various other interviews while talking about custom game modes for Battlegrounds, though he never suggested it would be part of the game's full release.
As for what is currently scheduled for the full launch of PUBG, Greene answered that in another answer, but include: User interface changes, bullet physics changes, vehicle debugs, audio remixes, online fixes and improvements, replays, and vautling.
However, Greene has gone on record to say that PUBG is being treated as an online service platform, and mods and other systems that allow for players to create custom modes and content are presumably a priority for the PUBG team.
Other little tidbits from the Reddit AMA includes a desire to implement a single-player mode (though no plans yet for such a mode), how there are currently no plans for a new project at the moment, and that there will be some new cars to go along with the new maps.
Since coming out in Early Access earlier this year, PUBG has become a bonafide phenomenon with millions of copies sold so far. It's no wonder that reporters pore over Greene's words for potential tidbits.