Touch typing doesn't involve the Escape key, really, which is the only key that's relevant here.
For those who need it, Esc will be readily-mappable to a hardware key combo.
Also, it's simply false that you can't use a Touch Bar key without looking down. It's just a simple motor skill like anything else. Very very slightly harder than having a hardware Esc key. Trivial.
I don't know about you but I "touch-type" F6, F7, F8, F9, F10 all the time while single-step debugging. It looks like the Touch Bar can change to anything at any moment, such as "answer facetime call" so I wouldn't trust blindly touching it. And I don't have a spare physical button to map escape onto because I already use all the remaining buttons for their intended purpose, including caps-lock.
Also - external keyboards are still possible!
I'm hopeful that the customization of TouchBar will have some perks that weren't quite made loud & clear in the preso.