I think this is the real answer. I have no doubt that Artemis will land astronauts on the Moon, and that there will be one or two or three followon missions. But with the fate of Apollo on my mind, I don't see how continued flights past that are sustainable. To me, the question is what happens after Artemis 4. Do we have a retrenchment like we did after Apollo (boo!) or do we support a moon base with cheaper options (yay!)?
The answer may not be putting Orion on a Falcon Heavy (F9 is out of the question)--I don't think it fits particularly well and I don't know if FH can throw something that heavy that far. However, if Starship's refueling-in-space plan works and Starship is one or two orders of magnitude cheaper to fly, then there will be tremendous pressure on NASA to switch over. Both of those are big ifs though. I don't count SpaceX out, but I want to see successful flights before I say that's the way of the future.
That political calculus may also change if global events change. For example, if China sets up a semi-permanent moon base, there will be tremendous pressure for us to follow suit. I would hope we would collaborate with the ESA a la ISS, but who knows.