Conversely, if these fancy chips become the standard mining kit, they will push regular hardware out even more. This means if you want to do a 51% attack there are much fewer individual people you need to compromise.

A 51% attack isn't based on the number of people, but based on computing power. If 30 people control 60%,then they control everything.

The more miners, the bigger the double spend required to compensate attack cost, the bigger the chances of it to be noticed.

I believe bitcoin is at the point where it is a financial loss to even try to compromise the network, even in case of success.