This is something I have been thinking about for a while. Social media services such as Twitter and Instagram could be recreated with an RSS like file format. This is a low tech solution but it has worked really well for blogs. Main difference to a RSS feed reader is that the social feed reader would render timeline similar to Twitter or Instagram. More detailed writeup below. It would be great to hear some insight from others.
RSS like file format to recreate Twitter, Instagram et al.
DAO's (Decentralized Autonomous Organization) would be a great replacement for twitter. Steemit is a example of this.
I think we should also pay attention to forums. Things like Twitter or Reddit are more transient and casual. Forums are much more suitable for serious discussions.