Software will replace physical placeholders

CDs, DVDs and Bluray disks are placeholders until internet bandwidth is cheap enough and strong enough all over the world, for us to be able to stream TV and Films. When we get there, we will no long have disks. 

Paper money and debit/credit cards are only placeholders, until we have all embraced payments on our mobile phones.

Physical books are placeholders, until we all fully embrace e-books

Point and Shoot cameras are placeholders until our phones can do a better job at taking pictures. In-fact we are already at that point where point-and-shoot cameras are getting phased out.

Therefore, SLRs are placeholders until they become phased out when phone cameras become sophisticated enough with the help of camera apps

There are many more examples

Our phone's software has made obsolete or will soon make obsolete these placeholders:

Alarm clocks

Calculator

Calendar

Photographs

Paper maps

mp3 player

etc

2 years ago, I told a friend that cameras are placeholders until our eyes are actually able to take photos. Then Black Mirror also suggests that our eyes will soon be able capture video 24/7 that we can rewind and playback either to ourselves, or through a TV set.

For more, look at  slides 33 - 84 here:

KPCB Internet Trends 2012