From the WMPU article:
Regular readers will know that we expected 2 updates to WP8.1 this year, GDR1 and GDR2.
Microsoft has however struggled to get the first update out, but now that it is finally happening, we are also seeing the first official sign of Windows Phone 8.1 Update 2.
According to Microsoft’s submission at the Bluetooth SIG, an update to the Bluetooth Stack will come with Windows Phone 8.1 Update 2, which Microsoft describes as:
The second major update to Windows Phone 8.1 expands the range of hardware options while simultaneously opening up the developer experience that enables even more fantastic apps. From the Bluetooth perspective, Windows Phone 8.1 Update 2 adds MAP, HID 1.1 , HOGP and Absolute Volume Control support.
As mentioned above, new is MAP (Message Access Protocol) which will allow a smart watch to access your text messages for example.
Also new is HID 1.1 Host support, which will hopefully bring support for Bluetooth Keyboards.
HOGP is HID over General Attribute Protocol, which allows smartphones to interface with accessories like smart watches or blood sugar meters.
Lastly Absolute Volume Control is a feature of the Audio Video Remote Control Protocol.
This is all consistent with what was expected of 'GDR2', even if the timing of the updates has slipped a little - with Update 1/Denim only starting to roll out about now, I wouldn't expect firmwares based on Update 2 to be available to user devices until April. Followed by a six month (at least) gap to some kind of Windows 10 release.
Is this timescale fast enough? Possibly not, though I've been over the external factors before, in detail. Great to see Bluetooth keyboards might be a reality on Windows Phone soon though - albeit a full decade after Nokia's older Symbian-based phones could do the exact same thing.
Not a criticism of Windows Phone per se, but more a comment on how insanely complex a job it is to create an entire OS, complete with support for every communications protocol, from scratch. It takes a while for every 'i' to be dotted and every 't' crossed. As the likes of Firefox and Jolla (and even Blackberry) are now finding out.
There's a link to the Bluetooth SIG in the source article, but you can't access it unless you're a SIG member, by the way.