The fatal flaw in your analysis is assuming that CGI is always cheaper than practical effects (or will be in the near future). This is wildly untrue. It is both cheaper and better looking to chuck a low paid stunt double through a fake wall during an action scene than it is to try to render that whole action scene through CGI, as one example. You are thinking of the huge practical action set pieces that certain directors are known for, but those typically take up under 5% of the runtime of a movie.

Yes, eventually in hundreds of years if humanity manages to avoid destroying itself then we may start seeing entire movies just rendered entirely in CGI and even characters down to the voice acting that are 100% digital and basically indistinguishable from real actors in real places but they didn't even use a camera at all to make it. Because its cheaper, not because its better. You can't get better than real if its done right. That's not happening in you or your kid's lifetimes though, after that who the hell really knows.