Posted in Droid-life's comments section earlier, this photo seems to depict a very large Motorola device next to an AT&T-branded LG G3. The G3 has a 5.5" display. This unknown Motorola hardware thus has a display substantially larger than 5.5", say somewhere in the 5.9" neighborhood maybe? So yes, this very well could be Shamu, the upcoming Nexus phone that we're pretty sure is going to be a thing in the near-ish future.
This Very Large Motorola Device Could Be Shamu, The Next Nexus Phone (Or It Might Not Be, We Aren't Sure) was written by the awesome team at Android Police.