"My mechanic had an interesting comment about a BMW convertible he was restoring. He said he thought he could get top dollar for it today because of the nostalgia factor, but the value will decline as those with an emotional attachment to that model age out/die. Wonder if this goes for guitars? (Sorry, can’t remember Year/model of BMW)"
No. If you consider the number of post-Boomer car nuts who go gaga over restored Gremlins and Pacers and Novas and Pintos (gag!), let alone 'Cudas and Cameros and GTOs and BMWs and Mercedes and all other autos from the 80's and 70's and 60's and 50's and earlier, you'll conclude that, as has always been true throughout human history, scarcity fuels desirability which fuels scarcity which fuels desirability which fuels....