According to the articles linked below, the successor to the Nexus 7 (2013) is going to be the Nexus 8 (2014). The change in form factor, they report, has to do with low sales figures for the former device as of December 2013, and with Google's desire to be competitive with the iPad Mini in a market flooded with Phablets and 7" devices.
Asus and Google are said to be working on this; the projected release for the new tablet purportedly will be in April 2014.
First link
Second link
Third link
Some of you might have seen this earlier story from last November which reported on a mysterious photo of the Nexus 8:
Link