Some of the code on the device is no doubt a copyrighted work, eg the main Glass APK and such. You can't dump some parts of Android without being root, and getting root would count as circumvention.
I'm sure they wouldn't pursue it... but it's shitty enough that they could.
But the measures that jailbreaking circumvents aren't intended to function as copy protection - they're doing something else entirely.
And even if those measures are protecting copyright in addition to locking down the device, has any court ever ruled on whether circumventing those measures without intending to breach copyright is a violation?
If a car manufacturer decided to lock the hoods of the cars they sell so that only authorized mechanics could access the engine, could they use the DMCA to outlaw users from circumventing the hood-locks on their own cars merely by printing some copyrighted text on the inside of the hood, and call it a copy-protection measure?
There was the DeCSS case, other than Sony's autorun CDs I think that would be the most trivial "DRM" but was still ruled a violation to circumvent.
Auto manufacturers, along with printer manufacturers, are already using IP in the on board diagnostics and printer cartridges to claim copyright violations when people adjust or replace parts "without authorisation."
Because the CSS code was there for the purpose of preventing unauthorized duplication of content, not to restrict people's ability to control the functioning of their DVD players.
Regarding printer cartridges, there have already been court rulings [1] that have determined that "jailbreaking" them isn't a violation of the DMCA, making the distinction specifically on the basis of whether the the element of the product being protected is "creative" or "functional". So we already know from case law that the DMCA doesn't actually prohibit people from circumventing functional lock-outs.
I'm sure they wouldn't pursue it... but it's shitty enough that they could.