Originally Posted by cyccommute

You do realize that we have been here before, don’t you? Shimano had an entire line that was cross compatible from 6 speed to 9 speed (with a few rare exceptions). I have bicycles that are running 9 speed mountain rear derailers with 9 speed…and even 10 speed…road shifters. I never went to road derailers with mountain shifters but it would not have been impossible.

Then Shimano decided to screw us by introducing a new drivetrain line that was incompatible. They will do it again, just watch.