Even if they got 51% of the hashrate they would not necessarily carry out a 51% attack, as doing so would essentially prevent them from every selling their equipment (GH/s again).
That is not the problem. The problem is that for the bitcoin to get to $100,000 per btc, you need to have blind trust in the network. And that includes trusting that there isn't a shred of possibility that there is someone crazy enough to do something stupid. And we know there are a lot of crazy people.
Scenario for you: China pays GHASH $1Billion to purchase the pool for the purpose of destroying bitcoin. $1B is nothing to China -- far less that the threat bitcoin poses.
You are correct over the long term, but over the short term it is not as much of an issue.
If ghash were to receive such a payment they could simply take the payment, announce it and the miners would simply leave. They would still have the payment and the network would be secure
You are technically correct. However, would someone want to put their life savings in a network where you have to trust that miners would simply leave. What if the "unknown" pool gets to be 50+% and it's really controlled by the China government?
The entire point for Bitcoin is that you "trust not a single party" but the entire network. However, in the world where it is so likely that 51% of the networking power could possibly be controlled by a party who we all have to trust... well, that breaks the bitcoin promise.
This is a serious, serious issue and the Bitcoin Foundation better be issuing a statement as to what they will do to remedy. Them staying quiet is also worrisome.