Steemit model is very attractive. Facebook and other tech giants have to adapt inorder to compete. I do believe they will introduce some sort of decentralisation and probably a coin of their own.
It will be a tough fight for them another problem they have is censorship. It appears people who do mot share certain world veiws are censored and banned from the big tech platforms that will also have a detrimental impact. Check out this shor blog post on censorship.

https://steemit.com/news/@daveboss/censorship