I might change my mind after some reviews come out and I see some full-res images from the K-3, but for the foreseeable future I'm probably sticking with my K-5 IIs and two K-01 bodies (and the K-7 which is largely collecting dust).
The reason I purchased a K-5IIs rather than waiting for the K-3 to show up is that I saw too many real-world side-by-side image comparisons between the K-5 IIs, the D7100 (another 24mp APS-C camera like the K-3) and images samples from the D600, D800, and 5D mkIII. To my eyes the K-5 IIs holds its own against all those cameras with higher-resolution sensors (meaning you cannot see a "clear" or "oh my God" difference in the images even when you pixel peep) except in two points:
-- Images from full-frame DSLRs have shallower DOF in some shots (a nice advantage if you want the shallowest DOF possible).
-- Images from the full-frame DSLRs have cleaner detail at high ISOs above 800 or 1600 (varied by sensor)
Granted, the K-3 has other significant advantages over the K-5/K-5 II/K-5 IIs beyond just the image sensor, but for me the image sensor (technically the image quality from the image sensor) is the biggest reason to switch camera bodies.
The reason I'm not immediately running out to buy the K-3 is that we're getting closer and closer to the point where the lens has a bigger impact on how much detail is captured than the sensor. Sure, higher resolution sensors give you a bigger file that you can crop more, but if the combination of the sensor and the lens isn't actually resolving more detail then all you get with a higher resolution sensor is a bigger file with the same image details.
Again, a full-frame sensor will give you the benefit of a full-frame perspective instead of a cropped view, better high ISO and shallower DOF ... but if you judge image quality in each new generation of camera by how much more detail is captured we're starting to get less impressive returns with each generation.
Unless the real-world images from the K-3 really surprise me I'll save my money and put better lenses on my K-5 IIs.