The Google I/O 2013 keynote touted some cool things to come, including a particularly interesting promo video for Google+ Hangouts that teased a refreshed Nexus 7.

Amid announcements regarding new Google Maps, updated Google Search, updates to Google Wallet, a unified Google+ experience and much more, a teaser video is particularly intriguing.

The promo video for the new Google+ Hangouts features a couple of seconds where the Nexus 7 tablet sports a glowing notification light, which is not present in any of Google's current tablets. Could this be the rumored next-generation Nexus 7 everyone's taking about?

Just 21 seconds into the promo video, the iPhone 5 appears to the right, accompanied by a Nexus 7 tablet on the left. While at first the slate looks like the regular Nexus 7, the glowing, oscillating notification light suggests it's a different model, possibly the next-generation Nexus 7. On the other hand, Google made no announcement in this regards during the keynote.

In other words, instead of answering existing questions about the next Nexus 7 this instance just raises new ones. If the video does feature a revamped Nexus 7 model, why didn't Google announce it at the conference? One theory is that Google plans to launch the new tablet model and put it in the video, but then decided to skip the announcement during the keynote. This possibility, however, doesn't seem very likely.

Another potential reason is that Google just added a notification light on the Nexus 7 in post-production of the video, simply aiming to demonstrate the capabilities of Google+ Hangouts.

Right after the 21-second mark the video also shows a second angle of the purported Nexus 7 refresh, when a girl picks up the slate to reply to a message. It's not very clear at this point whether the tablet she's holding is the original Nexus 7 or another model, but Google was not expected to completely change the design of the tablet anyway.

Rumors so far indicate that the next-generation Nexus 7 would sport a full 1080p display, a Qualcomm Snapdragon quad-core processor and the upcoming Android 4.3. Both the Nexus 7 and Android 4.3 were notable absentees during the keynote, but some still hope to see a "one last thing" moment toward the end of the conference.