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.