I have an interest for old bikes, long before most here were born. I get a lot of "those are cool". Won an award with one of them once. But the fact of the matter is there is limited interest in them and they sell for a "bargain" price compared your fancy Eyetalian machine from the 70's/80s. Fine by me, not complaining.
So what going to happen with those 70s/80s bikes? I'll stand by my earlier post, but I think the writing is on the wall. Electric bikes will be the thing in 30 years and downtube shifters will be regarded the same way as my Vittoria Margherita - quaint. "Manual" bikes will be an oddity, just like my bikes today. So if you are in it for the money, sell now or forever hold your peace.
"Comfort" brake levers, and stem shifters will be the friction shift lifetime winners.
I admire the Cambio Corsa shifter type as in "how did they conceive of that" Would never own one, as I am just not that flexible even for the "sport" version.
Never tried to use a Vittoria Margherita, interesting concept, but none around here to try.
When I was young, I admired the clever control Simplex front changers- I thought those were cool in their direct approach. I would have a hard time using one today.