Microsoft didn't invent this idea
You're correct, they didn't. And the Wright brothers didn't invent planes either but they made it work. It's the same for Henry Ford. Do you really believe he was the first to think of it?
At the end of the day it's irrelevant who first touched it. It's the ability to turn it into reality that matters. Apple made smart phones a reality for everybody, not just he geek in the IT office with a palm pilot.
The hardware has been available and/or in development since the early 1990's at least, and the software has been right with it
That would be like saying electric cars could be done 40 years ago. Maybe in concept but not in practicality. What would have been the point of having an electric car with a battery life of 10kms? Same goes for the eye tech.
I don't know where the "20 years" figure you quote comes from. The hardware is here. The software is here. The applications are available to anyone that can think of one.
"Within" is the key word in my 20 year statement. Yes and Yes for the tech but it needs to become main stream before we can call it a complete success. After all, if you recall the integration of UPnP (something much simpler than hololens), it only took about 10 years for most manufacturers to get it right. Virtualization is another domain that took time to become main stream. Today you wouldn't run a server without it.
So I think we both believe in the tech. We just have different opinions on how quickly it will be available.