I'm not sure I buy your point about ISA extensions. Many programs still target Windows XP or Windows 7, and if that "lag" remains the case, then it will be many, many years until vendors can reasonably require Windows 11 as a proxy for those ISA extensions. In the meantime, vendors can offer a Windows XP-11 version, and a Windows 11 "optimized" version, but at that rate, it would be just as much work to put the optimizations in the single version and make the program automatically detect the CPU, saving the user the trouble of figuring out which version they need while also making the CPU optimizations work on older Windows versions.