I've heard that Windows 10 will be the last version of Windows but it's only supposed to be supported until the year 2026 which is only 8 years from now.
But that is for extended support. The Mainstream support for Windows 10 is supposed to end in the year 2020 which is only 2 years from now.
I'm sure that they'll eventually be another version of the Windows operating system at least after the year 2026 so I'm sure that Windows 10 won't be the last operating system Windows releases for our computers.