Well, I think a new microarchitecture means a major bump. So between that and version bumps to to actual major software features, you get to 11 within 13 years or so.
Also, GCC 9.x compatibility may seem minor to some, but is significant for others. I also think there's some C++17 support in kernels - that's something too.
Ooh, I missed those. Support for C++17 is pretty major. Thanks. Perhaps my memory is fuzzy, I just remember the CUDA 9->10 switch having some significant (but not major) performance and feature changes.
Also, GCC 9.x compatibility may seem minor to some, but is significant for others. I also think there's some C++17 support in kernels - that's something too.