I cannot count how many times I've purchased something and shortly after a newer model came out, or there was an amazing sale, or the company stopped supporting it. This is normal. A company will announce a new product when they are ready. I've worked with MrSpeakers as a company on multiple occasions and Dan has been a real stand-up guy. I'm sorry that you feel cheated in this situation, but there was nothing wrong with the way MrSpeakers handled the announcement and release of the new MDP.
I recently ordered headphones internationally from Italy, and if the manufacturer were to release a newer version of the product I would not feel cheated in any way, as my model is still excellent. I have owned the MD 3.0 and know first hand that the MD 3.2 are excellent headphones. The MDP is not an upgrade to the 3.2, it's a whole new headphone.