So much of you remember, there was an article by 9to5mac, which went over some of the rumored features of WatchOS 6. One of these is surprisingly the built-in App Store app that you can walk from your wrist.
This made me think, you know how in WearOS, (Google's own watch software) has the Play Store built into the watch? Because of how it is structured, you can easily download apps without the need for a phone app, since the app does not have a store page, unlike the Watch app on the iPhone. You need to sign in to a google account on the WearOS app on your phone to make it work and it happens on the setup section, do you know when you first set up the clock? Now, this part is unlikely, but here's my theory: Assuming Apple makes an app on android after announcing this feature (and if they announce that the app, but knowing Apple, very unlikely), there is no doubt that apple would try to do it on WatchOS 6 when you first set up the clock.
For me I say next year because it can be loosely ending to get either another variant of WatchOS or another WatchOS version compatible with other phones in the market.  I think this is my theory, I could go wrong on this, but knowing Apple, I get better in error. I mean, it's worth saying though.
Edit: Troubleshooting issues. Written this on my phone.