[rodan01]

Windows Phone OS looks great in the Lumia 1520 with its 6-inch display. I think Microsoft should use Window Phone OS in the 7-inch form factor.

Rumors are that WP will be free for OEMs or as cheap as Android (after license agreements). Microsoft is proposing to use the same hardware for WP and Android and even allowing dual boot phones. The same strategy could be expanded to 7-inch tablets. OEMs could market WP tablets as cheap or even cheaper than Android tablets using exactly the same hardware. WP would shine in tablets with low specs.

The L1520 has 3 columns of live tiles, but live tiles are 20% smaller compared with the Lumia 920.
In a 7-inch tablet tiles would be about the same size as in the L920. So the 7-inch form factor is perfect for the WP start screen with 3 columns of live tiles.

The common aspect ratios in WP phones are 1.66 (15:9) and 1.77 (16:9). Most 7-inch tablets have aspect ratios of 1.6 (16:10) or 1.7 (17:10). I don't know if this could be a problem, but I suspect most apps are supporting multiple resolutions after year since the launch of the HTC 8X and Ativ S which introduced the 1.77 (16:9) aspect ratio for the first time in WP.

Apps in a 7-inch tablet would need to be scaled 20%-25% compared with the 1520, not a big difference.

I like Windows 8 in tablets, but the OS needs good specs to run smoothly, which is a problem for most part of the world population that lives in emerging countries. Windows 8 is more powerful but at the same time more complex and hard to learn. I'm convinced that a Windows 8 tablet is just another category of device compared with iOS and Android tablets, the best answer to compete with devices optimized to content consumption is Windows Phone.

Probably Microsoft couldn't get a good user experience with Windows 8 in 7-inch tablets, so there is none in the market, and they took the decision to promote WP to bigger screens. I suspect in q1-2014 we will see the first tablet running Windows Phone 8.1.

[abel920]

No.
Windows RT running on a Windows Phone however is AMAZING, and this will be the case in 2015 with WP8 being upscaled to have the functionality of RT.