The image you see above is a slide displayed during a session on high performance audio in Android. The tablet in the middle appears to be a Nexus 7, but it looks slightly different from the model that is currently on the market. It seems like the shiny trim around the device's bezel is now totally missing, while the top and bottom edges are slightly curved instead of being as straight as they are on the current Nexus 7 variant.
Of course, this could be just a render used as a placeholder and not an actual second-generation Google Nexus 7. Besides, the evidence is presented to us in low resolution, so we can't quite make any solid conclusions without further clues. If you feel like taking a look at the source of the image yourself, we've embedded the video with the presentation below – make sure you jump straight to the 38:30 mark.
Thanks for the tip!