Just Survive will apparently not be shut down any time soon as the developers, Daybreaker Games, will attempt to simply put it in maintenance mode while trying to figure out a way to reintegrate it in Z1, which is the PC version of H1Z1.
Here is a quick history lesson for those not up to speed. Daybreak Games originally launched a game simply known as H1Z1, which was later split into two - King of the Hill and Just Survive. The former kept the "H1Z1" prefix, while Just Survive dropped it, and seeing how it was the less successful game of the two, was expected to be shut down.
Now according to Jace Hall, the game will not be shut down, but will instead go into "maintenance mode" for a while, probably due to Daybreak's obligations toward Z1: Battle Royale, which is another renaming of the original game, only on PC. Once Just Survive is out of this maintenance mode, the developers will be looking into improving the game and then integrating it into Z1, as a game mode.
Those who bought skins in Just Survive were probably worried what was going to happen with their invested money, but Hall reassured them that none of it is going to go to waste. What's more, they might even profit from their belongings, since there are skins in Just Survive that are not present in Z1. The kicker here is that owners of these exclusives skins will be able to sell them to Z1 players, and limited supply almost always gets inflated prices.
The need for this kind of development becomes more obvious once you learn that the community started calling the developers "TheyBreak Games" in protest to several changes which eventually ran their games into the ground. Just Survive appears to be one of them as the most recurring wish from the players seems to be bringing Just Survive to its state from 2016.