I've already been posted about that Nokia will release a 6-inch Windows Phone Phablet, but now it looks to be "almost" confirmed. It will be the first phablet running on Windows Phone. Windows Phone 8 doesn't support 1080p resolution yet, but the rumor says that the next big update of the Windows Phone OS will come in the end of this year and it is said to support larger screen resolutions. Nokia will have an event in September too (A lot of events in September!), where they probably will show us this Phablet.
Windows Phone Central can now confirm a few things about this story. The phablet will be a 6 inch, 1080p, quad core device with gdr3 and a 20MP camera. It will be reportedly very thin with a slight camera hump akin to the Lumia 925. The tablet, a separate device, will be RT based.
Source: Reuters: Nokia launching large smartphone next month [Update] | Windows Phone Central