I don't know why they would want to trick us. The theme of a Rise of Kunark expansion is very plausible given the success of EoF.
Last time they pushed out their advertising info immediately after the EoF name was leaked, which sort of burned them because some of the things they touted as features, or the way they described them were not what actually happened in the release. I bet they learned their lesson and are being tight lipped and ignoring the leak this time to make sure they know exactly what they're adding to the game before they market it.
(The link to the trademark search is from your session, so it doesn't work for others. You can search for Rise of Kunark using the link on the page that loads.)