The Nokia Lumia 520/521 are extremely popular due to their functionality combined with low prices. T-Mobile announced they will be releasing the Nokia Lumia 635 as the first device sold in the US loaded with Windows Phone 8.1. The Lumia 635 has a 4.5 inch ClearBlack display, 5 megapixel camera, 1.2 GHz quad-core Snapdragon 400 processor, 512MB of RAM, 8GB of storage, microSD card, and 1830 mAh battery.
The Nokia Lumia 630 is nearly the same as the 635 with a matte finish and a dual-SIM model option. MSRP looks to be between $159 and $189 for these devices.
I am personally much more interested in the Nokia Lumia 930 that looks to be a Nokia Lumia Icon with a GSM radio and cool looking back options. It has a 5 inch 1080p display, 20 megapixel PureView camera, 1.2 megapixel front facing wide-angle camera, 2.2 GHz quad-core Snapdragon 800 processor, 2 GB of RAM, 32GB of internal storage, and Qi charging for its 2,420 mAh battery. It will be available in bright orange, bright green, black, and white.
The Lumia 930 will be priced at $599 and will start rolling out this summer. Unfortunately, the Nokia website states this does not include the US. Hopefully, this just means that the 930 won't come here, but that T-Mobile will launch something like a Lumia 935. I love the Lumia Icon, but need a T-Mobile version.
Nokia also announced that Windows Phone 8.1 will be included in their Lumia Cyan update. This Lumia Cyan update will launch this summer and include some additional Nokia features like improved Nokia Camera, Dolby Surround Sound (Lumia 1520 and Icon owners), third row of Live Tiles, and more.