The article doesn't seem to be on the Pop Mech website yet, and all I have is this months' subscription edition. The article is on pages 128-132 in the "DIY Auto / Future Collectibles" section. The factors for their choices were things like novelty, rarity, historical significance, and "most important", the potential for nostalgia.
Without typing out the details for each of the other choices, some of other entries were the Hummer H2 (which made the list as an embodiment of the vehicle of the 2000's Type-A mentality with a conspicuous need for consumption and flaunting tax write-offs - I'm paraphrasing, but you get the idea).
The Pontiak Aztec - for those with a bizarre nostalgia for the ugly duckling.
The 2002 Cadillac Eldorado - for it's "crisp, tuxedo-lke timeless styling, high-tech but handsome interior, 300 hp Northstar V-8, and low production numbers...
...and other entries including the 2nd gen. Toyota Prius, Chrysler Magnum station wagon, Scion xB, Plymouth Neon, Honda Insight, and Jaguar XJR.
For the Vehicross, these were their comments:
"There's a distinct possibility Isuzu will be out of business as of this printing, and the SUV that's easily it's most outrageous offering - The Vehicross - will be somewhat collectible. Probably the purest concept car to hit series-production since the Viper or Prowler, and, in spite of brilliant styling, sales were in the toilet. Regardless, you can't see a Vehicross and not do a doubletake."