If I were a member of SAG-AFTRA, I would certainly do everything I could to fight for the right to not eventually be replaced by an AI. And I think this issue goes beyond monetary interests. It speaks to questions that are far deeper.
An analogous battle once took place on the Broadway stage. At some point technology had advanced to the point where musicals could replace orchestras with high quality recordings. To do so would certainly have saved a lot of money. And some theatergoers might not even have noticed the difference.
But there would have been a difference. Local 802 of the American Federation of Musicians fought long and hard to not be replace by machines. And our collective theater-going experience is far richer because of their victory.
The same goes for human actors in movies. There is something beautiful in the bond between human performer and human audience. It would be a shame if that bond were to end up being broken, or replaced, by some technological alternative, simply in the name of cost-cutting.