Hope that the VX might be in GT4 also:
This is cool behind the scenes video of the making of Gran Turismo 4... Notice, at the 35 second point, there's a line of scale models used for 3d renderings... and there is a Isuzu Vehicross in the line up...
Fingers crossed. GT4 is going to a great game! But it will be the best if they squeeze the VX in there.
http://franck.paul.free.fr/gt4spc2_qt.mov
-Dave