The screenshot was shared on the NeoGAF forums and users went to work translating it. The notes describe it as the "second generation" of the Xbox One and some of the hardware specifications are also shown in the leaked image.
This leak comes after Xbox head Phil Spencer hinted at possible hardware upgrades to the Xbox One earlier this year, although he later retracted this statement. The leak also follows another recent rumor that reportedly leaked some FCC filings from Xbox while they were testing new hardware, which the FCC did approve and file. NeoGAF user ekim, who also shared the leaked image today on NeoGAF forums, documented the FCC filings and found that a non-disclosure agreement would expire on June 25 which may very well end up being a surprise release at E3.
It's looking more and more like the Xbox One Slim, or something like it, will be rearing its head sometime this year.