I didn't find any official information on this despite much speculation in other threads, but I think it's reasonable to expect a release or announcement in the next few months. The next tablet is currently called the "n900" by this community.

If you want the n810 wimax for it's looks, then go ahead. I suspect by the time I get wimax in my part of the country there will be a better wimax tablet.

Unfortunately for anyone considering buying a tablet, the next tablets will feature an omap3 for much improved performance over the previous tablets. I bought the n800 only 3 months after I bought my 770 because of the n800's increased performance. I think we're in the same situation now. I'm eagerly awaiting the next tablet for its major performance boost.