Nokia mentioned it would launch at least one WM7 mobile this year.
That said, N8 was announced in April last year, since all the newer Symbian v3 are based on same hardware platform. It wouldn't require more R&D investment to produce one or two more mid/high end handset before WP7?
E.g. X7?
Nokia did state in the Feb 11th announcement, that even if they are transitioning to Windows Phone 7 for their smartphones, that there are still Symbian based phone models in the pipeline, before they'll stop making them.
What they'll be named remains to be seen, as no new models have been announced in a while, but the hardware is probably very much like the C7, N8 and E7, with minor variations.