A popup message now appears to every WhatsApp users on Symbian OS:
Unfortunately, you won't be able to use WhatsApp after 31/12/2016 because WhatsApp will no longer support your phone.
It seems WhatsApp will be retiring its Symbian-dedicated servers and thus the app will no longer work after that. While it is a sad moment, we have to still applaud WhatsApp for its prolonged support for Symbian OS.
WhatsApp's departure from Symbian doesn't mean the OS is dead, but it's surely another nail in its coffin.