Firstly the video - I brought my K-5 primarily for stills and it is stunning for that. Made a very small video at a concert in Samoa earlier this week. Video is not completely useless - in fact it is ok in quality etc, but if you are buying the camera specifically for video then there are other options that might be more suitable, and more widely used in the DSLR community for video (more support).
With regard to the future K-5 replacement - I have recently brought the K-5 and asked myself the same question. Right now (until the end of the month) the K-5 pricing is really good. All the early production problems have been fixed, and you would be getting a superb camera at a very good price. What might be on the next model - better video, more MP - better IQ, better AF, maybe twin memory cards. I have found the K-5 more than my needs in each of these areas, so went for it. Honestly, unless you are planning to print the size of a roadside billboard you are never going to need more MP than the K-5 currently has. The IQ of the K-5 is stunning already - it really rocks in that area.
You will know what your requirements are - but if you wait for the latest and newest, you will never buy a camera - there is always another one around the corner.
Once you do purchase the trick is to use it lots, learn it throughly, and then make great images. Any of the current cameras on the market is good enough for that - the issue is not using the camera enough to learn its strengths and weaknesses.
There is no prefect camera - but the K-5 is good, and a lot of camera for the money.