I assume Chevy will announce details at the press days at this coming week's Detroit Auto Show (press days start 13 Jan). But cars.com just started listing 2018 Bolts this morning. Not saying they're in a dealership yet, just saying they're listed on cars.com.
National inventory had dropped to about 2,450 Bolts from a high near 5,500, so the arrival of the 2018 model year was kind of overdue. Still plentiful where I'm at, but I understand there were empty lots in some high-demand locations.