There was a price drop in Japan on the D3x that would amount to $6700 US retail price. Soooooo if that price drop happens across the board, I think that will give Nikon the ability to bring a D700 sized camera out with the 24MP sensor. Right now, I think the price diff between what the D700x would be and the D3x is too far apart for it to be really feasible (and since there's not been any D700x yet, I think Nikon must concur). However, with a price drop, I'd give it 6 months and I think a D700x would be announced - probably between $3000 - $3500.
Now, they might NOT bring out a 24MP D700 style camera at all and go for a D700s with the current D3s sensor in it. If they go that route, I'd say 9 months(ish). Wait too long and you announce it too close to when the D4 / D400 come out.
Of course, the D700 might be all ya get for now too (although I'd LOVE to see that 24MP sensor in a smaller body - My D3x gets a bit heavy after a long hike)
That's my take anyway, and it's worth every penny you paid for it
