interesting question, since all the rumors have been regarding a full screen video iPod and (to a lesser extent) a Wi-Fi iPod.
I don't think we'll see any new iPods until the pre-Christmas shopping season. I mean, they'll have to have new gear for that, and to introduce something now would mean two significant updates inside of 6-8 months. (Possible exception: if they introduce full screen video now, it would be priced above current 5G iPod with Videocome x-mas, they could fold full screen into everything from $299 up. Kinda like how they brought color screens into the product line).
As for the nano, I don't see them adding video (although how sweet would a full screen nano video be!). And I don't know if flash RAM prices allow higher capacity now. Eventually it will, thoughagain I'd say pre-Christmas '06.
In addition to WWDC, lots o' folks expect some announcement of new product for Apple's 30th anniversery, which is April 1st.