There are a lot of assumptions in this next story, so take it with a cup of salt, but regardless of the speculation, the picture of the device is worth perusing. The above shot which was leaked by @evleaks is of a device called the LG Isai. It is a device that is heading to the Japanese telecom KDDI. The reason this is relevant is that it is very possible this will be the same or similar design for the LG G3, and/or the next Nexus smartphone.
Last year, the same thing happened. The Isai from last year turned out to be the same general/basic design for the G2 and a little bit for the Nexus 5. Of course, we don't know for sure that the G3 will follow this design, nor do we even know if LG still has the contract with Google for the next Nexus phone.
What's especially noteworthy is the flat-style configuration of the back buttons. They are much more subdued than the G2 was. This adds an attractive aesthetic appeal, but we wonder if the usability might be hampered.
