Well then you need to be clear about what you want. You want continuous support for the lifespan of your device. You can't expect a new OS to limit itself to the confines of older devices. For example, we have all seen the problems on the N900 caused by having such a small root partition. I can almost assure you that the next Nokia Linux device will not have that problem. That means that the OS will be able to have a lot more stuff on / without having to hack an optification solution. The result of that is that the next OS, whether it is MeeGo or Maemo 6 will likely not fit on the N900's tiny root partition. Forcing MeeGo (or any future Nokia OS) to restrict itself to the confines of the N900 is frankly unreasonable, in my opinion.

However, demanding full support for the lifespan of the device is perfectly reasonable. But then the question is, what is the expected lifespan of the N900? Unfortunately, I don't think that is written any where. And that is something we as a community should demand to know.