There's plenty of times where it shouldn't have been possible for a sequel, but they retconned something to make it possible. There's also the prequel route, or of course the different world/characters but with shared elements and references to each other (a la Final Fantasy).
I'd bet that if it had been a hugely popular game selling 10m or something that the franchise would have got some kind of continuation, whether it be a direct sequel or something else.
No, I mean it's physically impossible to make a sequel to it. The game is lightning in a bottle. Ueda is semi-retired so it can't really be done.
Seems you have a different definition of impossible to me. I define it as "can't be done", while you seem to define it as "can't be done in the way that I'd want it to be done"...
Dunno who ueda is, but it really doesn't matter, anybody is replaceable. Fans may not like it as much, but that's never stopped big franchises continuing beyond their creators before...