I don't think the 8v will ever be collectable, it was bottom of the 'GTI' range anyway and not a well loved car when new, now that most of the good ones are in the hands of enthusiasts they can be made in to the cars they should have been at the start, but collectable?..i don't think so.
In fact i would say that the 8v makes a perfect 'project' car, plenty of cars to choose from, cheap to run and fix and you don't have to ruin something rare like an anni/vr and to a lesser extent a 16v.