People always want to run their divices on the latest software. I am always wondering about that. Nobody belives a 1970 xt computer capable of running Windows 8.1 with 640k memory and a hard disk of 10 Mb, but when a new operating system of a phone demands 1 G instead of 512 Mb the world is too small and MS is the worst company ever.
I got a real laugh out of this one. While the basic gist of what you have said is true, the dates, numbers, and facts don't match. An XT computer didn't come out for another decade. I got my first XT in 1982, and there was no such thing as a 10MB Hard Disk, you used floppy drives. In 1970, storage medium consisted of reel to reel tapes and punch cards. Been there, done that. Worked on the main frames. I got my first 20MB HDD in 1985, and had the largest capacity of anyone I knew personally. I was the envy of all my friends. They thought, "How will you ever fill all that up?" Yeah, you can laugh now.
I got a 200MB HDD in 1986, and it was over $800 back then.
Okay, back on topic. Yeah, I fully expect my 635 to upgrade without any issues. Is it because I just expect inferior hardware to work forever? No, it's because Microsoft said it would. I don't expect to get the camera features that the PureView lumia cameras have. So what? I didn't buy one of those. I do expect to have the new movable keyboard, with the pointer stick, and better Office apps, better outlook, better Skype, and the ability to run Universal Apps as they are published to the store. Of course, apps that require minimum 1GB to run, I won't expect to run. I don't expect it now because I know I have a 512MB device.
I'm not worried about this one bit. Fragmentation? That's only going to come from carriers that refuse to let the upgrade go through where the end user refuses to jump on the preview to get it anyway. If you really want it bad enough, you can get it. I've got WP8.1.1 on Preview, and am REALLY happy with it compared to regular 8.1. Less resuming for me, and other features that have been added I really like.
About the fragmentation problem:
The whole point of Windows 10 is to eventually do away with the fragmentation issues. By rolling out updates free to everyone for the supported life of the device, then, as Microsoft said, it will come to the point that asking "What version are you running" will be meaningless, because everyone will be on the same version at some point in the future.
Yeah, there are still people trying to run Windows 95 and I've seen a couple on Windows 3.1 and DOS still (yes, even today), but those people aren't trying to get modern apps and surf the net. One precious lady running Windows 95 was just using a very, very old copy of MS Word to write her memoirs for her children to have one day. Had an old 14" CRT monitor that made my eyes hurt. Somehow I don't think those kind of people will really have an impact on the overall applications market. Before long, people are going to be treating XP and Vista the same way they do Windows 3.1 and Windows 95 right now. They simply won't continue to write applications for them. No worries.