I would probably just get an excellent condition D200 for much less, if I were you. I doubt there's all that much in the new D300 that's both worth the extra $$$ and the extra wait. If you go for the D300, you'll first probably want to wait out any initial production problems before buying unless you're the adventurous type (like me perhaps

). Even if you don't wait, it might be very hard to get your hands on one for the first couple months if not longer. Heck, even the D200 continued to be regularly out of stock at most reputable dealers for over a year after its initial release -- and the same seems to happen w/ most Nikon DSLRs other than their entry level D50/D40/D40x line. If you really do want to get it at initial release, you might need to try superstores by phone (or online) like Circuit City or Best Buy as they seem to be able to stock sizeable batches even early on -- though they don't usually last more than a couple days or so. That's how I bought my D200 at the initial release date.
Save the $$$ on the body and put it towards more/better glass. And then, maybe wait until Nikon eventually puts out a full frame semi-pro body before jumping on that for the higher price, if you want FF.

I'll probably just stick w/ my D200 until Nikon does that.
RE: the MP count for the D3, well, it's not *that* surprising. They were never competing for MP count in that market segment before anyway. Besides, this D3 might well be more like a D3h w/ a possible D3x (w/ higher MP count) to come later. It sounds more like a competitor for the Canon 1.3x crop 1D line than the FF 1Ds line so far. The only thing missing is the "h" at the end.
Anyway, the final offical announcement of a FF Nikon body makes me less interested in buying another APS-crop lens now -- well, certainly nothing expensive anyhow. Will have to see. Might be nice to save up for that newly announced 14-24 f/2.8 for instance.
_Man_