No, it's more complex. First off, it's non-trivial to upgrade people's existing Android app data which makes it problematic for Jolla to issue it as a SW update => lots of care mail that it can't handle.

Second, there might be quirks in media codecs etc that break existing apps as 4.1.2 was not a happy moment for Qualcomm.

Third, there might be issues that only appear on SbJ and there wouldn't be money to work on it.

It could run on Android 4.1.2 HW adaptation and I think I've had that working before.

To conclude, the only way it could only be available would be in unsupported form and developer/technology preview kind of thing.

Of course, that depends on the interest by people* and if there's money to actually work on it.

(* I really wish we lived in a world where people could stuff money into a bond that gets paid out to a company in case a company gets something done; without the overhead of credit card processing, etc..)