Even though FM Radio was supported in Windows Phone 7.x devices, Microsoft didn’t support the feature in Windows Phone 8 OS so far. It was reported that Microsoft didn’t have time to port the support to the new platform. There were reports that Microsoft is working to bring back FM support to Windows Phone 8 devices. The Verge reported that Microsoft will enable FM Radio support for compatible devices such as Lumia 920, Lumia 820 in the upcoming General Distribution Release (GDR2) update for Windows Phone 8. The update in expected in May-June time frame.
Nokia is also planning to bring no.of improvements as part of this release such as double-tap the screen to wake the device from standby, flip to silence option, and Lumia color profile settings for the device screen.
Source: The Verge