About 3 years. By the time Windows 9 rolls around, Microsoft would migrate to ARM. If you want to run your old x86 Win32 programs, use an emulator. The FOSS world will move to ARM or MIPS because there is no binary compatibility problem that plagues closed source software. The legacy chip lost its benefits. Now that 64-bit code is popular, x86 doesn't even have the code density advantage anymore. It won't survive long with bigger code, less registers, irregular encodings, more baggage, useless decoder complexity, obsolete 16-bit modes, higher engineering costs, and higher chip prices. Even Intel has an ARM license these days.