I don't think they are assuming that. My guess is that they're looking for the best return on their money, which I assume would be what we currently get.
Don't get me wrong. I like the idea of better made retro stuff, and there will be people like you who would buy into that, but aren't buying the new replicas.
The problems would start if too many people bought the retro's, then wore them for several years, rather than buying a replica each season.
They could obviously charge more for the retro's, but how much more would they need to charge to retain the cash flow balance?