So, there is going to be a new announcement for two new bodies - Canon and Sony in 2 months? OK, so let's say that the announcements actually come out on schedule. Then there is the additional 2 months or so, for the cameras to actually arrive at stores for sale. Do you want to be an early adapter - the first one out of the box? no reviews? no other users indicating what is good and what is not? If you really don't want to be an early adopter, and wait to read several reviews - wait another 2+ months to decide.
That brings us up to about 8 months from now for acquiring a camera. Then, there will be yet another camera (or 2 being announced). You are right back to square 1.
Let's say that you go with a K3 as you indicate. In 2 or 5 or 8 or 12 months will it suddenly stop taking pictures because of the new announcements, deliveries, reviews? No, it will just chug along taking pictures as it has has always. What will be the differences? Really, can't say - because we do not know what the new announcements are going to announce.
Here is a real example (just 1 sample point, me). 2010 (September 20th) Pentax announces the K5. Great camera - first shipments go out. Then the sensor spots are reported (all camera manufacturers have QC problems Nikon with dust, etc.). Reviews come out - great camera, sensor spot problems get resolved. About a year later, I see the price drop for a day sale at $750, well I buy it (announced price was $1700), next day it goes back to $1K. A year later the K5II/K5IIs are announced. Good upgrades, but not worth trading in my K5. A few months ago the K3 is announced - a great camera, wonderful reviews, but my K5 is still chugging along and I see absolutely no need to go with either the K5II/K5IIs or the K3.
So, my 2 year old camera with 3 year old technology - counting that it was used in the Nikon D7000 - probably going on 4 years now - it is still taking wonderful images. No problems - they were all worked out by waiting. Saved a ton of money on the price - it came down from $1700 to $750.
I still have my K100D from about 7 or 8 years ago. It is still taking wonderful pictures too!
I would do my homework, select a camera, then stop reading about any other camera other than the one that you selected - only continue reading to see how it works. Nothing else matters. Now, if you think that the K3 is the one that will perform best for you. Solid reviews and no reported problems, and several months of operating history. That just indicates that it was a solid selection on your part. I would just go with it and forget about all the rest. New cameras, new announcements - really do not matter. They only matter up to the point that you actually buy. After that they are all a distraction - they are marketing pitches to get you to dump your current camera and to go with the new one.