I can't tell if you are being sarcastic or serious. But tape is no where near dead as backup media for business.
I'm serious, but you are right. In the near future, spinning disks will be used for the same applications and seen as the dinosaur of technology: backup and low-performance works.
The truth of the matter is that spinning disks are simply to slow for modern day technology. Compare your laptop when using a 7200rpm disk or an SSD. Compare your Oracle database query times when using a legacy storage vendor or an all flash array that can do 1 million IOPS . It is the performance aspect that matters in modern day computing. The bottleneck is storage, not your CPU, not your memory, storage.
It makes all the difference, especially in transaction-driven enterprises. But sure, for backups you can use spinning disks or tape. Just as our modern cars run on dinosaurs, for every legacy technology, there is still a usecase. I like to run my MSX emulator once in a while :)