Good Morning,
I too am still using the K20, and I really do like it. It has been a very dependable and reliable camera. Overall it does suit my needs, however there are a lot of instances in which I could certainly use the K5's additional capabilities (low light, ISO 80, Dynamic Range, better AF, disabling DFS). Early on the $1,700 price was a barrier. Now that I have the funds sitting in my desk drawer (and the price has fallen), I find I still have not pulled the trigger. I would like to see the direction that Pentax is going to go, and what new capabilities (or possibly upgrades - they will have in the new whatever). I see the price has broken the $1K mark again in some retail outlets. So in some respects, I have kicked the can down the road to speak. I am patiently waiting for Pentax's next move, before I make any decision. That said, I would like to have the opportunity to make a somewhat informed decision while I can still get a new K5 - only because I have found the supplemental Pentax extended warranty very worthwhile (one came with the K20 that proved to be very useful).
I do think that depending on the type of photography you do, the price difference is reasonable. I do a lot of ambient low light in the evening, so that would hit all the K5's sweet spots for me. However, it changes for each photographer....