Google Nexus 10 Root and bootloader unlock is now Possible

XDA developers released the Samsung Nexus 10 ToolKit, which allows one to do lots of neat stuff with the device.

This ToolKit can root your  Nexus 10 and unlock its bootloader, should you ever want to flash a customized ROM on it. There's also a backup feature included in the ToolKit, so you can dump your apps and data to a computer and then restore them in case anything goes wrong with your tablet.

Source (XDA)