There is this remarcable image of being left behind when Christ returns. And those left behind are not saved in any way.
Now consider the final verses of Rev CH21. Isn't it said that even throughout the Millenium, the doors of New Jerusalem will stay wide open? Rev 22:14 and 15 shows that you have to get there to gain access to the tree of life. Outside of NJ is nothing good to be found (V15) WAKE UP ITS IMPORTANT!
Now consider what the return of Satan to this world will do. It says that he will go out to gather GOG AND MAGOG. Yes that´s what the JW Bible says too. So those who the WT pretends have atteined human perfection are called Gog and Magog here. Astounding, no?
Now it becomes utterly (horribly) clear, that JW teach a false gospel. You have to be born again to see the kingdom of God. There is no way around this. Without access to the trees of life, one will be out of the boundaries of the "promised land". We have to be adopted out of the children of Adam to become spirit-begotten children of God. Flesh and blood will not inherit the kingdom of God (or incorruptibility as DS correctly pointed out!)
JW s need help, they need it so direly. Those who believe they see, albeit being blind, are in a very bad position.
God bless