1. Flash storage is a thing - Boot drive, gaming drive, SD card or anything
2. Optical drives will probably survive if they pack some insane amount of storage space in a small form factor. Whatever they do, they will be too slow and only good for deep archiving.
3. Mechanical HDDs will linger a few more years and then completely die, unless some niche appears, where they are better. Alternatively, some insane new technology might speed them up (but not very likely).
4. Tape drives will outlive all of us :D They are still alive and developing.

There is a huge difference between home use and pro use. Home use will go completely in the cloud, while pro will remain on local storage. There will be a totally distributed network of computers, holding random bits of data, but it's too hard to predict what shape or use it will take. I suspect it will take a tiered approach, where fastest and most accesed data will be on flash, while least accessed data will be on tape or some future version of Blu-Ray.

Also, keep in mind that the definition of a true "backup" says that storing same data on at least two different physical locations, stored on two technologically different medias is considered as backed up.