Why would Nokia manufacture 2 almost similar products simultaneously, when they know that you would be as happy with N810 that you are with N800. It costs money and they don't want to spend it.
I don't know why you cry about this? If there will be a new ITT device after 2-3 years, I'm sure it will have lot of new features like wimax etc. You can use your N800 till' that day. And generally I think that lifetime for all consumer IT products incl. mobile phones is about 2-3y anyway.