Microsoft has already had, and has, high end phones from Nokia. We've read good things about the hardware. The cameras are good. But it seems as though few people care.
The problem is that people just don't like Win Phone. It's not whether it's equal to Android or iOS. It's simply whether people like it. It could be the most sophisticated OS in the world, but if people look at it and think that it's harder to use, or they don't like the way it looks, or whatever, they won't buy it. More high end phones won't fix that.
WebOS had the same problem. People would pick it up, play with it for a few seconds, and
put it down again. I've seen people do that with Win Phone as well. They aren't interested in spending time to figure out how to use it, and the truth is that it's not as obvious as Android or iOS.
It's also from Microsoft, and I believe that people are tired of Microsoft. They feel they still need to use Windows, but they don't want to use it for mobile as well. This is a mountain Microsoft has to climb over.
In addition, it occurs to me that there are still a number of Nokia loyalists around who are buying these phones. They care less about the OS than the name on the phone. But now that Microsoft owns this, they are slipping away. I had mentioned this before Microsoft completed the purchase. I believe it's still true.