Nokia is currently developing the new successor for the Windows phone series. They call this new gadget as Nokia Lumia 710. In some countries, you can start purchasing this new gadget but in Indonesia and some other Asian countries you must bit more patient. Below I found a nice review of the Nokia Lumia 710 from techie-buzz website.
Along with the Lumia 800, Nokia also announced a mid-range value-for-money Windows Phone Mango running handset, the Lumia 710.
Internally, the Lumia 710 is similar to its elder bother the Lumia 800. It’s powered by the same 1.4GHz Qualcomm Snapdragon processor and Adreno 205 GPU.Externally, the handset is mainly made of plastic, and sports a 3.7-inch ClearBlack display with WVGA (480×800) resolution. The back cover of the phone is also swappable.