You could just shoot with what you've got now instead of waiting.
Yesterday I was shooting my D7000 and just marveling as I thought about what it was like to shoot weddings with the D100. You had to absolutely nail exposure or the photo was bound for the trash bin. But if you got it right the images look great as an 11x14" print. 6MP (and really bad MP by today's standards) were enough for us then because it's all we had.
I'd never go back because the extra forgiveness of the D7000's dynamic range makes for a better life. But if I'm honest, the D90 gave me similar performance at $400 lower price. If image quality was the only concern, it would have been silly to upgrade from the D90 (and that's the closest you'll ever hear me come to saying I have buyer's remorse for buying the D7000—for the record, I have never regretted a camera purchase).
In the end, upgrade decisions are (or should be) based on an extremely complicated and personal analysis and, like TTJ said above, until more is known about a possible D400 it's really hard to discuss the original topic of this thread.