Microsoft recently made a half-hearted statement about producing hardware for two years. I don't think that a commitment to an annual upgrade is part of their plan right now.
Apple, for the last number of years, has provided an upgraded device or two on a very predictable schedule. It is part of their SOP, and will remain so for the foreseeable future.
Well said.
Also if Microsoft was to do that, where would we have room for OEMs like Microsoft wants? What would be the point of them making a W10M phone if Microsoft has plans to always allow you to upgrade with their own plan? Windows Mobile users are already small (but maybe not smaller than BB), and even somehow having half of those users (just choosing a number) would be a lot.
Maybe I'm overthinking it, but that's how I see it.