In the coming months Mozilla will launch support for an open ecosystem of extensions on Firefox for Android on addons.mozilla.org (AMO). We’ll announce a definite ...
Firefox Mobile supported add-ons for many years, but due to having to change some things under the hood a few years ago, add-ons got restricted a bit (though you could still use them).
They're basically announcing they finally fixed the issue and they're coming back.
They don't spell this out, but my interpretation is that extension devs will be able to publish extensions for use on Android, without Mozilla explicitly approving each one of them.
Many desktop extensions work as-is on Android, so when this goes live, we'll likely see dozens, if not hundreds, of extensions becoming available in the following weeks.