I have already been waiting a VERY long time. But your points are valid and logical. And I am also of the opinion that there will be no D400. The D7100 has a magnesium alloy body and has been called the 'flagship' DX body. How much can you read into that? I don't know.....but....those things taken with the fact that a D400 is loooooooong overdue and currently not even being hinted at.....it doesn't look good.
So what am I left wanting that the D7100 doesn't provide?
1) D200/D300 size/build/layout. I love it. It seemed natural from the first and now I can't imagine anything better. Could I get used to the size/shape/layout of D7100. Of course. But I never felt like I had to get used to the D200.
2) The expectation that the D400 would have a better frame rate than the D7100. Pure conjecture of course, but not an entirely unreasonable expectation.
3) The feeling that I'm getting _everything_ I could possibly want at a commensurate price. That is the way I felt when the D200 came out. I can't think of a single specification that disappointed me or that I found lacking. Maybe that was just a lucky coincidence based on my desires and a very robust semi-pro body. But it sure felt good. I consider the D200 one of the best purchases I have ever made...of any type. I want to feel that way about my next camera.
So, I can get a D7100 or I can continue to wait on the less and less likely everyday D400.
Pro's and cons:
If I get a D7100 and the D400 never comes out them I probably have the best DX body Nikon has made. No downside there. No regrets. Whatever limitations the D7100 may have cannot be remedied until its replacement comes out.
If I get a D7100 and then the D400 comes out? Take a loss and sell the D7100 then get the D400. Or rationally assess my needs and if the D7100 is adequate, keep it as my primary body and save a lot of money.
Wait for the D400 and continue to use D200. Not the end of the world. I'm still getting images that make me happy with the D200. But as you say, I'm missing the sizeable advantages of the latest technology which could be getting even more fulfilling images.
I'm starting to lean towards the D7100. But I'm still not in a rush. The idea of what a D400 _could_ be makes me willing to wait just a little longer.