Back in early 2016 , WhatsApp announced in a blog post that they will be dropping support for BlackBerry OS, BlackBerry 10 OS, Nokia S40 and Nokia S60 series devices.
Now it seems the company has a little change of heart. The company has now updated their blog post which was about dropping support for these operating systems. Now in the update, the company has mentioned that these devices will get support of WhatsApp till 30th June 2017. So this clearly meams that the WhatsApp has given 6 months time users to these OSs to upgrade to newer operating system.