How many will listen to tape and vinyl in the next century?


Something between 500 and 1000 people, maybe?
inna
How many? Take the highest percentage pure copper in speaker cables, consider the remainder percentage, apply a coefficient far less than 1, multiply the result by the worlds population at 2100AD and obtain an overestimate proportional to the coefficient.

Possibly my grandson, he is now 1 and 1/2. Maybe other grandchildren who's grandfathers have a vinyl system that they hear at early age.

Interesting, I believe there are turntables that could be maintained for that length of time, vinyl disks also.  
I am still in 20th century too and will remain there forever. Interesting how we try to bend time, subjectively.