Vintage carbon isn't really a thing... yet. One of the reasons is the constant advancement in carbon technology. Today's low end carbon frame is typically stiffer, lighter and more comfortable than a top of the line model from 5 years ago. I have a 2011 Tarmac SL2 and I love it, but it doesn't compare to a new Tarmac SL4.
When early carbon does start to become collectible, I think only select models will ever be desirable. The Tarmac will be too common and outdated but an S-works for instance, will always carry a certain cachet. I think the same could hold true for your Colnago.