As warned earlier, WhatsApp is finally going to stop supporting devices that run an older version of Android, iOS, and Windows Phone. This step by WhatsApp is going to affect a minor segment of users as most of the Android, iOS, and Windows users own smartphones that run higher versions than Android 2.2 Froyo, iOS 6, and Windows Phone 7. For the users who still have a device that runs an older version of the above mentioned Operating Systems, WhatsApp will not support your device anymore.
In an official blog post, WhatsApp said that the older versions of Android, iOS, and Windows Phone do not "offer the kind of capabilities we need to expand our app's features in the future." This move by WhatsApp is to ensure that it offers pervasive services on all the smartphones. The older versions of Operating Systems are not capable of handling new features introduced by WhatsApp such as Video-calling, Voice Calling, and more.
To recap, Android 2.3 Gingerbread was released in December 2010, which means if your smartphone is not older than five years then WhatsApp's new policy won't affect you. For the iOS users, it is an even lesser concern as the only iPhone not to get upgraded to iOS 7 is the iPhone 3GS, which was launched in the year 2009.
For the BlackBerry OS, BlackBerry 10 OS, Nokia S40, and Nokia Symbian S60 users, WhatsApp is going to support them until June 2017.