A lot of information has already been revealed about what Windows 8.1 Blue will bring to x86 PCs. WMPowerUser reports of features that will come with Windows 8.1 RT, and eventually trickle down to Windows Phone Blue as well.
Justin Angel has been hard at work dissecting leaked images of Windows 8.1 (x86 and RT), and has made some interesting discoveries. Windows RT is much more similar to Windows Phone than Windows 8 Pro, simply because both of them are customized to work on ARM chipsets. It's very likely that new features in Windows RT may trickle down to Windows Phone. Our belief is further backed by a Microsoft Job posting from February which states that the Windows Phone team is "leading the charge to bring much of the WinRT API surface and the .NET Windows Store profile to the Phone." WMPowerUser reports that new features for Windows RT Blue should make an appearance on Windows Phone Blue as well when it is released later this year.
According to Justin Angel, Windows RT Blue (and hence Windows Phone Blue) will add support for new features such as Bluetooth 4.0 and Bluetooth LE (low energy). On a side note, one of the leaked features of Android 4.3 includes Bluetooth LE as well. Windows RT Blue will add support for a range of accessories such as heart rate monitors, etc. The next update might also bring support for VPN (Virtual Private Networking). A new API for Low Lag Cameras will allow for more easy capture of HDR images, surely a new feature for Windows Phone Blue.
There is no guarantee that these features will actually make it to Windows Phones and RT powered devices with the next (Blue) update, but Justin Angel has provided us the best picture so far of what Microsoft has in store for us in the near future. For more detailed information, hit the source link posted below.