By 2050, the few survivors of WWIII will be living in huts and hunting with bows and spears.
I doubt whether the next period of total global war likely to commence before 2050 will use nuclear weapons.
Conventional and cyber will be the most likely weapon technologies, with nuclear held off due to the possibility of retaliation with bio doomsday weapons.
Even a second rate power should be able to wipe out upwards of 95% of global population with bioweapons. After all, Australia was able to kill that high a percentage of the rabbit population twice decades ago.