WhatsApp stops on 31 december with the support o.a. Windows Phone 8 and BlackBerry OS/BlackBerry 10. The chatapp remains on those platforms work.
That the support this year it would stop, it was already longer known. At the time, it seemed that WhatsApp on the outdated operating system after the stop of the support would not be able to use, but that is not the case.
The functions are somewhat more limited than on for example Android and iOS. As you can no new WhatsApp-accounts or current accounts to re-authenticate – for example on a clean installation of your mobile.
Support also stops for the Nokia S40 series, and Android versions older than (and including) Android 2.3.7. WhatsApp recommends to upgrade to newer operating systems. It usually means that investing in a new device.