I agree completely.
There are going to be 7B people online in 10 years. That is a lot of people who will be using different applications on blockchains. There will be a ton of social media sites all doing their thing.
Even on the STEEM blockchain, Steemit is not going to be the main application. With the introduction of the SMTs, you are going to see a ton of apps show up, many that will be more popular than Steemit.
In fact, we might see a facebook type application designed on the STEEM blockchain that is better than any of the apps on the EOS blockchain.
Who knows? It all comes down to who has the better app and what people embrace.
EOS should be a tremendous system...yet from what I understand, aspects of it can be drawn into the STEEM blockchain if the development team chooses.