Well if you are familiar with Nokia's way to sell products i.e. mobile phones, it's not a miracle. N810 has been developed on the basis of N800, so there is no reason why to continue manufacturing the old product. That's just the way it is.
But I agree that there is a certain kind of philosophical difference between N810 and N800, that might mislead people to think N800 would continue. For the future: it's absolutely sure that next Nokia's ITT model will replace N810.