I dont think they should stop hardware changes. Technology is always improving and new hardware upgrades are necessary. If N900 had the specs of the N800 would it ever be as popular? I doubt it...iphone has hardware changes too but its mainly built the same, making upgrades possible, Nokia cannot do this because they have different types of phones, not just 1 like the iphone. Android phones are also basically the same. Nokia has business phones, media phones, and internet-centric phones, and basic dumb-phones. they cant all have the same software because they're entirely different devices with different purposes.

Also, the n900 was somewhat of a test-run for Nokia to get feedback and things, so i dont think it will have a long life, or future support. i think they're maemo 6 devices which will be more refined will have more support for updates and things.