Actually the Coinbase announcement is a big setback for the "Segwit2x movement". It means that the Segwit2x supporters will have a very hard time to convince ordinary users that they are "the Bitcoin" and not "an altcoin". That is crucial for them, because otherwise ordinary users (those that don't have a clear stance in the block size question) would continue to use the legacy clients.

I think with this announcement Segwit2x is almost dead, because as an altcoin it would not survive (or only as a very small coin) and Big Blockers would use Bitcoin Cash instead. The only chance Segwit2x still has is to achieve 90% of the hashrate for a long time (that would need miners with really big pockets), or attack Bitcoin in a way that forces the legacy chain to hard-fork to another algorithm.