I agree with your points and can only guess as well. I'm in a position to buy now, but the D7K is not quite what I want, and the D300s is starting to look like more $ for less sensor in comparison. So, in my case, I will probably continue to shoot my D200 and wait.
If the D4 tech advancements are not scheduled until the fall of '11 - and Nikon desires to get the full DX lineup refreshed sooner than that - then perhaps the D300s gets an earlier update and the D4 technology will be rolled into the FX camera lineup later in the year.
OK Nikon, may I have a D350 for Christmas this year?