There will be pro versions of Windows with Win32 support for as long as there are programs needing it. That doesn’t mean a simpler consumer version is a bad idea.
There are two alternatives for the future (20+ years) of Windows:
- Only Windows with Win32 support for around $100 and UWP practically dead. The only new software made is some specialized pro applications. Hardware selection is limited and have a high markup. Home and general office users have moved completely to Android or iOS, that has evolved to push away Windows.
- A UWP focused Windows exists as an alternative to Android/iOS. There is plenty of Windows hardware and most new apps got a Win version. There is also a pro version of Windows (at around $100 compared to the free basic one).
Alternative 2 is better even if you exclusively use (or sell) Win32 apps, as there will be more hardware at better prices. As a bonus you will have the common consumer apps available if you need them.
Everyone should wish for UWP to suceed, even if you prefer Win32.