Sorry, no excuse for MS not supporting less than 1 year old devices on new OS. Do you actually believe they had no idea what wp8 was going to be when they released wp7.5 mango? Really? You think Software development time is less than a year? WP9 and w9 is already being developed. There is already a set of deliverables that the OS WILL have, and what they are thinking they can drop. There are always add-ons in the end which is what pushes dates back but its because they are listening to their customers and observing their competition.
Problem with apple supporting older devices in my opinion is that they do not tell people how much it will slow their ip4. Apple knows, they have to. They know exactly how it will effect battery, speed, and every other aspect of their older hardware. You think they put a DC 1.3ghz chip in the phone because its has 50% headroom? No, they put the cheapest slowest chip that they can get away with. All manufacturers do this. I would still take a slight hit to speed if I could run the newest apps. WP8 has to have more apps than wp7.8 so that is the biggest reason I want wp8. My phone screams, it can stand to lose 25% of its speed to run wp8. Sure, original hardware owners may not be able to run wp8 very well, but just like the ip4, those devices are now over 2 years old. Realize that you are holding antique (in the land of technology at least) hardware.