You have no reason to regret... there is no camera like the k-5 out there that is suitable for my needs... the ergonomics, the sensor size (hence file size), the features (TAv, multiple exposures, in camera HDR, two dials and WR). Enjoy your new toy and focus on your technique rather than worrying about the camera/lens. There is always a new model coming up no matter what happens.
If the lens price goes up, that may be a good thing... I have the same combo... beats Canikon equivalents hands down... 18-135mm is tack sharp even wide open. If you can't take good shots with this combo, it is likely your fault, not the camera/lens