Is the D7000 a D90 replacement, or an addition to Nikon's product line? There is certainly more of a difference between the D7000 and D90 than there is between the D80 and D90 -- enough so to see it as a new camera coexisting with the D90.
(1) At current pricing anyway, the two cameras are at very different price points.
(2) Accoding to Nikon's web site, the D90 is still in the product lineup. This isn't surprising, though. The D200 was still available new and still listed as a current product after the D300 had been out a year.
(3) The feature set between the D7000 and D90 is at least as different as between the D5000 and D3000, both of which coexisted in Nikon's product lineup.
Surely the D7000 will remain in Nikon's product lineup after the D90 is discontinued. But it's not clear to me that the D7000 will replace the D90 in the lineup, or that the D90 is about to be discontinued.