Well, I should correct you about '40 years': actually, the x86 ISA was born in 1978 with 8086 CPU, so it's just 30 year old.
Next: Of course, the x86 ISA is not an ideal architecture, but it is global dominating one. Do you know that English is not an ideal human language? Ask about it to Chinese-, Japanese-, Spanish-, French-, German-speaking people. Do you know that C and C++ are not an ideal programming languages? Ask about it to Pascal-, Basic-, Assembler-, Python-coders. What for I'm talking these? There is a standard de-facto notion exists. And if anybody (you, me, AMD) would try to break this standard, then this revolutionary would fail.