cresloyd

Given that it takes several weeks to process a passport renewal, and I have to send off my current passport with the renewal application, would I not be able to travel abroad while I wait for my new passport to arrive?

And what would happen to people who live in one of those states whose licenses are not yet REAL ID compliant, and their passport is about to expire? Will they still be able to get through TSA checkpoints for inside-USA air travel somehow, if they send off their old passport and are waiting for their new passport to be issued?

Nyet.

Extensions for lots of states expire next month.

Per this:

Starting January 22, 2018, passengers with a driver’s license issued by a state that is still not compliant with the REAL ID Act (and has not been granted an extension) will need to show an alternative form of acceptable identification for domestic air travel to board their flight.