Exactly, I don't believe that there is some hardware limitation that just makes it impossible for Nokia to create a version of Maemo 6 that works on the N900.

It also may well be in Nokia's financial interest to do so. Obviously Maemo, and perhaps especially Maemo 6, is Nokia's answer to the iPhone. One of the things that has made the iPhone so profitable is the app store and iTunes, a source a revenue that extends well beyond the sale of the device itself. So you want to keep people engaged and happy with the device they have, so they keep coming back to purchase the other software based goodies. If people feel like they're being left behind after only a year, on the N900, their next device may well be an iPhone, WinMo phone, Android phone. They won't have as much of a reason to stick with Nokia and Maemo and so Nokia will lose the revenue stream from that customer that would go to the Ovi store, etc. Look at the crazy dedication people have to Apple products. Apple doesn't get there by leaving people behind. But if leaving people behind is what Nokia does with the N900, then it will risk remaining a niche product like the N95 and other high end smart phones of Nokia's past, rather than break out the way the iPhone and Android have.