That's what most concerns me- the VAST majority of people do not care one ounce about decentralisation, so when FB shows them their shiny new blockchain I think the hype and momentum there would be incredible.
Until someone gets their account frozen. Then they might start caring.
The thing to remember is that companies are only interested in blockchain as a cost-saving exercise. They don't care about the benefits to their users. Once users realise they can get some real benefits by using a proper cryptocurrency, they won't look back. Hype and momentum are temporary. Substance is what counts in the long run.