I don't think E7 and N900 fall in the same category. Not to say that E7 is a bad device, but 16GB internal memory with no SD slot instead of 32GB+SD? And upgradeable? How would that be? I don't think Nokia expects it's endusers to know how to flash a phone... How about the tonns of payed for symbian apps? When are they ALL going to be ready for meego? Since they would have to be transferrable.
Maybe the next gen device won't be called N9 but surely E7 either.

I think/hope that it's gonna have x86 CPU, hopefully a 1.5-1.8GHz Intel Atom Moorestone. If it's not at least 1.2 I won't bother upgrading for now even if the other specs are nice. My N900 is quite good now