The generally reliable @evleaks is reporting that Samsung is working on 10-inch and 12.2-inch tablets, each with a resolution of 2560×1600.
The claim appears to be confirmed by SM-P900 and SM-P600 user-agent profiles on the Samsung site which match the resolution. GSMarena also pointed us to an Indian shipping website which appears to show prototypes of two versions of the 12.2-inch tablet entering the country.
Given the screen size and resolution, it seems more than possible that the 10-inch tablet is the new Samsung-made Nexus 10, while the 12.2-inch monster may be a new Galaxy Tab or (gack) a Windows Tablet. If so, the smart money is on the latter being released at the IFA in September.
Apple, FWIW, is working on a 13-inch tablet, or so the rumor goes.