Originally posted by pericombobulation The release dates just say July, but WHEN in July?
Even if you get a more definite release date, that doesn't mean you will be able to have one in your hands by that date, depending on your location. You can't change the date of your trip, but Ricoh can change the date it starts shipping the K-70.
Originally posted by pericombobulation I'd like to make some large prints when we get home
I just made a very detailed 12" x18" print from a photo I took with the 16MP K-30, the K-S2 will be fine for resolution, either of the K-3's will be even better.
Originally posted by pericombobulation I had been debating between the K-S2, K-3, and K-3 II
In my opinion, it depends how important the flip screen is. K-3ii is probably out of your budget and you might be kicking yourself for the next few years if its successor is a major upgrade. Depending on how important better AF and better metering is, and whether or not you mind the extra size and weight of a flagship DSLR, if you can get an original K-3, that might be your best choice for a similar budget as the K-S2 or K-70.
Originally posted by pericombobulation Low light performance, also with respect to cost.
The K-3 and K-3ii might have a slight advantage over the K-S2 (and your K-30) and even if you can get a K-70 soon enough, it may not be much better than the K-3. There has been some discussion about how the K-3's sensor is noisier than the K-5/K-30 sensor because of higher pixel density, but none of your choices are going to match the K-1's low light performance and in my opinion, the biggest obstacle to taking good low light photos with any of your choices is perceptual. At high ISO values, you can't push or pull the image as much in post-processing, but any of your choices (and your K-30) will give you amazing low light photos if you remove some mental barriers.
Originally posted by pericombobulation So I don't know how important Astrotracer will be, nor even really how well it works.
Finding night skies in Europe with minimal haze and light pollution is going to be a challenge. Unless you find a castle in the Alps or a mountainous region of the former Yugoslavia, you are likely to be SOL on this trip. Now, if you really think you want to make astrophotography a hobby
and you want Pixel-Shift, then you might want to start campaigning your finance department to make an investment in a K-3ii. Use the argument that "I'll be buying a new, relatively expensive camera in the next year or so anyway, so why not get the K-3ii now?"
In summary: don't count on getting a K-70 in time, if you really think that's the camera for you, take your K-30 on your trip and wait another 6 months to buy a new camera. If the lack of a flip screen isn't a big deal and you like the K-3's features, snag yourself a new one while you still can. If the flip screen is a big deal and you can't wait for the K-70, then get a K-S2 now.