Or simply stop adaptation on a larger scale.

No, by transactions, they mean transactions on the block chain. That is, only 7 people in the entire world can buy things with Bitcoin every second.

HFT markets would use off-chain transactions, like all current Bitcoin exchange markets, so wouldn't be affected by this in the slightest.

You have no idea what you're talking about. Trading on the blockchain is insane and no one is really attempting to do it.