If the project's chief engineer is openly referring to the car as "Chevy Bolt" in statements, I think it's likely Bolt is the final name.
http://www.autoblog.com/2015/06/24/chevy-bolt-testing-video/
http://www.autoblog.com/2015/06/24/chevy-bolt-testing-video/
"Effectively these are the bones of the car that's going to be the production Chevy Bolt," said Josh Tavel, the car's chief engineer.
"We really wanted to convey the notion that this is running fast. It's happening," said Pam Fletcher, GM's executive chief engineer of electrified vehicles.