According to WhatsApp’s FAQ page, only those smartphones which work on Android 4.0.3 or newer operating system will get WhatsApp support from January 1, 2020. That is, if your phone runs on an operating system older than Android 4.0.3, then from next year you will not get the benefit of this Facebook-owned instant messaging app WhatsApp. Not only Android, the company while giving information about iOS devices said that from next year, WhatsApp app support will be available only on iOS 9 and newer versions. Apart from this, you will be able to avail the benefits of WhatsApp only on KaiOS 2.5.1 and newer versions.
If you use a phone that runs on a version older than the above and is not eligible for these future updates, you will not be able to avail the WhatsApp service from January 1.
According to the report of Mysmartprice, WhatsApp will not release updates for iPhone 4 and older phones. These models do not support iOS 9. Apart from this, Android phones which work on older operating systems include smartphones like Samsung Galaxy S2, Samsung Galaxy Note 3, Sony Xperia Z1, HTC One M7, Moto X and Xiaomi Mi 3.