Decentralization is not a feature for the end-user, it's a feature to developers. It's probably impossible for a new social network to take on Twitter, Facebook, etc. directly. However, a decentralized social network allows startups to move far quickly and implement other features that the big social networks are lacking.
I suspect that whatever social network eventually pushes out the dominant players today, will use tools like these.
One good precedent for this is AOL. AOL was safer and more user-friendly than the world-wide-web, but the web's decentralized nature allowed competitors to spring up much more quickly. I suspect something similar will eventually happen to today's social networks.