According to information found by dataminers, it looks like the next map coming to PlayerUnknown's Battlegrounds is a snow covered map, with the current title Dihor Otok.
PC Update 21 for PUBG, which is currently available on test servers, is a pretty huge patch, and people digging through it have found a bunch of information which has not yet been officially announced by developer PUBG Corp.
According to this thread on Reddit, the update seems to contain the first map images for Dihor Atok, which — if the dimensions here are accurate — is smaller than Erangel, but larger than Sanhok.
The map appears to be snowier at the top, and features more towns at the bottom where there is less snow. It's just like real life! With extra guns. The datamine information also suggests that C4 is coming to PUBG in some capacity, thanks to the discovery of a 3D render in the game files. A further selection of leaked images can be found here.
The map is due to release this winter, appropriately enough, and will apparently introduce other new mechanics that are yet to be discovered...