Interesting subject and one that will have the most lasting effect on the replica industry.
Personally, I feel that, as others have said, consumerism has played a huge role in the amount of luxury goods that are replicated. I do not, however, think that this will negatively affect the value of gens sold. Corgi used the example of Louis Vuitton purses. While it is true that many are replicas, most people KNOW that many of these purses are replicas. In fact, there are parties where people get together, socialize, and exchange/sell replica Vuitton purses! As such, I feel that pushes gen luxury items to new heights and, in my opinion, even higher values. In the 70's and 80's, Rolex, Omega, etc. were recognizable however nowhere near as recognizable and scrutinized as they are today. The latest James Bond movie, for example, was one of (if not the) highest grossing Bond movies ever. The Planet Ocean is given loads of screen time and while this is not the only reason the Planet Ocean is sought after, the movie made people outside of the watch world aware that "that's the Bond watch!".
With the media saturation we have become accustomed to, there are hundreds of watch/luxury item advertisements and product placements that have become sought after (and, of course, replicated). As such, I feel that as media saturation and bombardment will only cause Gens to be even more coveted than replicas and even elevated the status of Gens.