I think we could be almost 100% sure that the new Pentax, to be unveiled this summer, will have the same sensor as the K20D. I suspect that nothing will be changed in this department. All other hardware will be improved such as the body, the AF, the Prime processor and the FPS.
This is based on what Pentax said in the past when the K20D was announced. There was not enough R&D budget to tweak the whole camera, so they used the K10D as a basis for the 14,6MP sensor, including some minor tweaks (larger LCD screen, better mirror dampening). Maybe the sensor will be revised a little, but earth-shattering differences are not to be expected.
I like the new shorter prism in the leaked photos. Now there's more room to have Pentax prominently on the front of the camera