To take the camera to higher than the existing 3fps will probably need a new sensor with faster readout capability as well as a different processor system, shutter, mirror etc., etc., etc.
I believe that the next iteration upwards from Pentax will be a completely new body design with totally new innards. It will be (or already is?) a major project for them and they will have to make it sooner rather than later just to stay in the game. I don't believe thay can sit on the fence much longer, even though most users will never use or need the improvements in frame rate, but improved fast tracking low light AF is an increasing must.
I won't even comment on the possibility of a larger sensor. That, I'm sure, is in the mix with the new high end body development.
When it will appear is anyones guess, I suspect they may make a pre-announcement at either Photokina or probably PMA next year just to keep the brand in peoples minds and the LBA hunger moving forward. I suspect that Pentax will also make a big play on new lens releases until then.
What I believe will surely happen soon, will be a basic entry point DSLR, and that it, and the K200D, will soon sport a Samsung CMOS sensor with live view in both models with improved performance tweaks on the K20D design to bring the LV AF performance into line with the competition.
I know that us traditionalists see LV as somewhat of a gimmick, but I believe that it is an essential marketing requirement as well as SR. All the manufacturers are aiming at the transistion from P&S users into DSLR users.
I wouldn't be surprised to see manufacturers dropping the mirror and prisms in future models! They did it with viewfinders to cheapen the products, I can see the same happening with DSLR's as it's a big cost area.
The next 2 years will be interesting, to say the least!