WPCentral, citing unnamed sources, have revealed the 4 screen resolutions of Windows Phone 8.
They claim the OS will support 480×640, 480×800, 720×1280 and 768×1280.
The first resolution would presumably be for a device with a front-facing keyboard, while the rest suggest traditional slate devices.
On the higher WXGA resolution they quote Phone Arena as saying "…on a 4.5 inch screen, the pixels per inch would come in at 332, topping the 326ppi reading of the Retina Display on the Apple iPhone 4". Sounds tasty.
The continuing support of WVGA is of course noted, and suggests at least screen resolution will not be a barrier for an OS update.