From the N800 -> N810 transition, I'd say N810s might drop to 200, but that's all. Of course, this will be a substantially bigger advance, and the N810s seem to be out of production, so maybe nobody will have stock at that point anyway...

(Oh, and BTW, calling it N900 is likely to be wrong, and create confusion. While calling it RX-51 is not really more helpful than calling it N900, since it won't be marketed under that label, it is accurate, and doesn't risk causing confusion when Nokia does release something entirely different as a model 900 or N900.)