I wonder if any of the people watched the demo. They showcased Terminal, and there was an escape key on the touch bar. They also specifically said pressing the "fn"'key would show function keys on the touch bar, which is exactly what you have to do on current Apple keyboards to use the function keys.
It seems like a non-issue to me unless people simply don't like the touch bar not being physical keys, which is fine, because they can just get the other Pro without it.
I haven't. I based my prediction on the assumption Apple engineers are not stupid. For what I observe, it's quite the opposite.
The bar's function varies according to the application being used. It should be trivial to make, say, iTerm, which is immensely popular (I use it myself) have Esc and function keys available by default.
I am pretty sure that when you open a terminal, esc and function keys will be up there. It'll not be a mechanical key, but I'm sure it'll still work.