In an effort to promote the adoption of Android 10, Google announced a new policy: Vendors who want to get support for Google Mobile Services (GMS), after February 1, 2020, must upgrade their systems to Android 10. XDA-Developers reported that Google will stop OEM certification for legacy systems (including Android 9 Pie) after January 31 next year.
In other words, before January 31, we still have the possibility to buy a lot of mobile devices pre-installed with Android 9 Pie. However, after February 1st, mobile phone manufacturers who want to ship with Google Apps support must upgrade to Android 10.
For vendors, getting Google Mobile Services (GMS) is critical to the entire Android framework. It covers the Google series apps, local libraries, and services, and is an integral part of the Play Store. Obviously, in order to solve the fragmentation problem of the Android ecosystem, Google has also made great efforts to promote OEMs to update their systems more frequently, while avoiding the problems caused by fragmentation.