Why would a premium product increase market share? By definition luxury/high end products will always be a niche market. Otherwise Leica would be the biggest camera manufacturer & Ferrari will sell more cars than Toyota.
Besides Pentax already has a super premium product in the 645D (>10k). While a premium product may create a talking point & create brand awareness, there is no guarantee this will translate to market share. In the 90s Apple released the 20th anniversary Mac, which sold for US$10,000 - flopped big time. The company only turned around with the introduction of the iPod, which while not the cheapest in the market, was certainly very affordable. Nice design & great user experience was only part of the reason for its success, good marketing was also very important. So much so that the Steve Jobs reality distortion field became overused (IMHO) to explain Apple's success.