There is speculation that Google will ban sideloading in the near future, too. That is, it will extend its Advanced Protection model to mass-market Android. Then, sideloading will only be possible for that tiny minority of nerds like us who know how to use ADB and install an .apk over the command line.

I don't think the "but you can" rounding error alternate Android app stores and side-loading constitute a viable developer alternative. *

* Except in China, in which case it's only true for their domestic Android market