Apple has continued sales of old devices to corporate/educational buyers without making them publicly available in the past. The eMac and original iPad were both available to education markets far longer than public markets.
I can't find any corroboration for your assertion about the original iPad. Every source I can find says it was discontinued immediately in favour of the iPad 2. Selling off old stock to the education market isn't the same.
The main point is that it's not unreasonable to think Apple would keep products around for enterprise/education markets without selling them publicly, or at the very least without mentioning them during a high profile keynote.