The replacement for the K-3II - when it arrives (and we don't know when that will be) - will undoubtedly be a little more capable in a few areas, but more expensive than the K-3II is right now. Furthermore, as a brand new model it may have one or two minor issues that will need to be ironed out through firmware updates and possibly service updates. We've even seen that happen with the full-frame flagship K-1. Early adopters are always at risk of experiencing unexpected problems, and whilst most of them are quite minor, some aren't. If you wait for the new model, you'll run that early adopter risk, but more importantly you'll miss out on many months of enjoyment.
So, my vote would be to get the K-3II. And, if you can get a nice deal that includes a free lens and/or grip, even better. It's a proven, well-sorted camera that does almost everything very well indeed, and you'll love it. Alternatively, as has been mentioned above, consider a new or used K-3. Now that the KAF4 compatibility update has been released, the K-3 is future-proofed as far as lenses are concerned. All it really lacks compared to the K-3II is GPS, astro-tracer and pixel-shift resolution for stills photography - nice features, but hardly essential (do you really need them?). However, you do get an on-board flash which is useful in so many ways, particularly as a trigger for off-camera flash units.
Choice, choices