This rumour has been blown out of proportion by the crypto media. It is completely unsubstantiated - the Economist and Independent articles don't provide any evidence to support it. I even wrote a post analysing it - https://steemit.com/cryptocurrency/@pkcheese/facebook-will-acquire-coinbase-crypto-rumour-analysed

Yes I do think this partnership would be a positive for the crypto space and legitimise the industry, but there is absolutely no precedent for it!