All current Nokia smartphones (N8, E7, E6 etc.) support all GSM spectrums.

Or, do you mean technologies (CDMA vs. GSM)? Yes, Nokia's failing IMHO has been to ignore CDMA. However, there was a good reason for it, but it left the entire CDMA market open to Android (and Blackberry), until iPhone was made available on Verizon.

I really think Nokia made a mistake. In order to capture more market share in the U.S., the strategy should not have been to switch to an OS/ecosystem controlled completely by on U.S company, but rather to actually make devices for more than 50% (well, less I guess if you take it that until recently, most Nokia phones *didn't* support all GSM spectra, specifically AT&T) of the mobile phone market in the U.S.

But, some rumours seem to indicate that some of Nokia's first WP7 phones will be CDMA- or LTE-based, so maybe they are doing both.

But, if they won't have any CDMA-based phones, and no WP7 phones by Dec, while they have the N9 ready-to-ship, it makes no sense to just ignore the U.S. market for another 6 or so months.