The first Android Auto-equipped head units and vehicles started rolling out almost five years ago, but the Play Store client has just now hit 100 million downloads. It joins the likes of Google Home, Files, and others that have recently reached nine digits. While the app's future might be uncertain, it's still chugging along.
The Android Auto app is required on phones that connect to vehicles with Android Auto capability. However, it also has a standalone Auto UI for use in older vehicles. At I/O last year, Google started talking about the Assistant driving mode, which was supposed to replace the standalone Auto UI. Many users were unhappy with that possibility, of course. Now, Google seems to be in a holding pattern while it decides what to do.
In the meantime, Android Auto has crept over the threshold to more than 100 million downloads in the Play Store. That's the same group in which you'll find YouTube Music, Google Home, Google Pay, and many more. The app's popularity might be one reason Google has hesitated to push people over to the Assistant driving UI. Whatever happens, we'll probably find out this year.