At a blogger event in Hong Kong, Nokia announced that the upcoming Nokia Amber update for the Lumia 520, 620 and 720 devices will also bring Bluetooth 4.0 support which was previously supposed to come with Windows Phone 8.1 update later this year.
According to Nokia, Nokia Amber will bring Bluetooth 4.0 support, including explicitly support for Bluetooth Low Energy. The low energy standard is used to communicate with accessories such as heart rate monitors, fitness monitors like the Fitbit, and temperature sensors.
Though, there is not any official confirmation on this yet, but we expect that this Bluetooth 4.0 support will also come on Lumia 920 and 820 with Amber update. The Amber update is coming this August.