I think with a bit of good marketing, store presence and some positive reviews, this camera could do very well.
For the amateur/semi-pro, Pentax has a bit of a drawback in the smaller lens selection, lack of rental options, less developed flash system etc... Some people also perceive the lack of a full frame upgrade path and the generally shaky position of the brand of the martketplace as drawbacks.
For the beginner, none of this matters. The Kx will be the only camera in this price bracket to offer such an advanced AF system, such high FPS, HD video, so many in-camera processing options etc... This looks to be a brilliant camera for the money - if Canon made it it would sell like hotcakes. I really hope Pentax market it well, so I can stop worrying about them going bust