I believe the hardfork they are talking about is "Bitcoin ABC"
It's called Bitcoin Cash, and they have the support of Bitcoin ABC. It's basically the "UAHF" that BITMAIN were talking about.
bitcoincash.org.
I do respect that they're phrasing it like it's an altcoin and their development of BTC.
As soon as we saw the news of the ridiculous hardfork getting rejected by big exchanges the price started skyrocketing, along with BIP91 activation soon lockin segwit.
The price is absolutely no indicator of anything right now. It's just random and irrational speculation about Bitcoin's future and it makes no sense.
The users of Coinbase should have a right to their "Bitcoin Cash" in the same way that they should have a right to their ordinary coins. Otherwise, it's just glorified theft from Coinbase.
It's not theft if they announce it two weeks in advance.
People who hold their coins in Coinbase and pay less attention to their holdings (use the "Coinbase Vault" for example) might not notice the warning. Regardless of what happens there will be a huge amount of funds kept in Coinbase and Coinbase will potentially have access to a not-insignificant amount of UAHF coins that their users who didn't withdraw.
I have the impression it might be more of a technical decision, and not a political one
I think Gemini's stance on this makes more sense:
We will make every effort to support withdrawals of the chain with less total difficulty, if it ends up having a significant amount of hashpower, exchange volume, or economic value. However, unlike with the Ethereum / Ethereum Classic hard fork last year, we cannot yet guarantee that we will succeed in this effort, due to a lack of two-way replay protection in the various forks of Bitcoin Core (including Segwit2x, UASF, BitcoinABC, and Bitcoin Unlimited).
To not even commit to your users' needs like this is quite insulting, especially when they never bother to respond when people have their accounts frozen.