It is a common problem faced when switching mobile phone that cause previous Whatsapp chat message to dissapear in the new device. Although Whatsapp has rolled out several backup features in the past, the process is very complicated since it involves many steps to backup and restore the messages.
Recently, Android Police found that users can backup the chat message on Google Drive in the future! This feature also supports backup of photos, music, audio and even videos. You can restore these settings and media files into new devices with just few clicks! This feature will soon be available in the next update of Whatsapp from Play Store and Apple App Store.
Source: Android Police