The VX is pretty much a niche car and will likely never see any serious valuation above normal market prices within the next 20 years. Somewhere down the road it may gain some value, but very unlikely. There are rarer and more unique limited production vehicles out there that only extreme enthusiast have any interest in, and there all dirt cheap. A few examples: Toyota FX16 GTS, Mazda 323 GTX, Isuzu Trooper RS (1st Gen). Those were all "sleepers" and represented significant industry firsts (the Toyota was the first built in the US) or very limited production (1st gen Trooper RS only saw 2500 units) and yet any can be had for a pittance. If you can find one.

Buying a vehicle as an investment is an immediately suspect decision at best. The market is so fickle even for bonafide collector cars that it's truly the capital trade of the extremely wealthy. As a VX owner the true value of the vehicle is what it means to you, as an individual enjoying a truly individual truck.