The up/downscaling would be handled by the graphics chip, as it has to do that on a regular basis whenever rendering 3d-content that has a texture on it that is larger than it is displayed.
The easy reason why there won't be upgrades is that WP7 is not backwards compatible and that there are LOTS of people out there who would not be to happy having their phone upgraded to a version which would be unable to run any software they own, like e.g. Navigation Software.
Providing for a way back to the old OS would mean lots of extra effort by MS/HTC just to enable it. The experience would also possibly be quite bad as WP7 wasn't designed to deal with user removable storage.
Some people only get Firmware upgrades when they take their phone to a store because they have issues with it. Imagine someone taking his WM Phone there and they flash Android on it - it would be pretty much the same: EVERYTHING is different, your Software doesn't work and so on.
The Hardware of the HD2 wouldn't be a problem. The resolution of 800x480 is the default resolution of WP7, the 1 Ghz is what we will most likely see in several release devices and the ROM would fit into the HD2s ROM, as at least the leaked RC1 and the x86-Emulator-ROMs were smaller than e.g. Energy's ROMs.
The easy reason why there won't be upgrades is that WP7 is not backwards compatible and that there are LOTS of people out there who would not be to happy having their phone upgraded to a version which would be unable to run any software they own, like e.g. Navigation Software.
Providing for a way back to the old OS would mean lots of extra effort by MS/HTC just to enable it. The experience would also possibly be quite bad as WP7 wasn't designed to deal with user removable storage.
Some people only get Firmware upgrades when they take their phone to a store because they have issues with it. Imagine someone taking his WM Phone there and they flash Android on it - it would be pretty much the same: EVERYTHING is different, your Software doesn't work and so on.
The Hardware of the HD2 wouldn't be a problem. The resolution of 800x480 is the default resolution of WP7, the 1 Ghz is what we will most likely see in several release devices and the ROM would fit into the HD2s ROM, as at least the leaked RC1 and the x86-Emulator-ROMs were smaller than e.g. Energy's ROMs.