[Nexus 5 Accessories] Watcher07:
Let me try to explain this a different way. The BLE operates independently of the Profiles. A2DP is at version 1.2 as well as the HFP at 1.5. To put this in perspective, A2DP verson 1 came about in 2003, 1.3 was in 2012. BLE has existed since 2003 when it was Cyrix or something like that then became an adapted, certified bluetooth tech in 2010. But it doesn't matter because of how they operate. The following is taken directly from the bluetooth.org's developers PDF about A2DP:

In Figure 1.1, the structure and the dependencies of the profiles are depicted. A profile is dependent upon another profile if it re-uses parts of that profile, by implicitly or explicitly referencing it. Dependency is illustrated in the figure. A profile has dependencies on the profile(s) in which it is contained – directly and indirectly. As indicated in Figure 1.1, the A2DP is dependent upon the Generic Access Profile (GAP), as well as the Generic Audio/Video Distribution Profile (GAVDP) [3], which defines procedures required to set up an audio/video streaming. The A2DP defines parameters and procedures that are specific for audio streaming. The terminology, user interface and procedures as defined in the GAP and GAVDP are applicable to this profile, unless explicitly stated otherwise.

Bluetooth 4.0 uses GATT as opposed to GAP that earlier versions of bluetooth used. The A2DP profile doesn't do anything but state how to process the codecs, compression and how to present the output to a device. The GAP and GATT are core operations profiles that dictate things like power usage and such. When you pair two bluetooth devices, (since we're talking about v4.0 here I'll use 4.0 terms) GATT keeps the phones connected but without drawing alot of power by utilizing the BLE hardware chip. As soon as A2DP gets triggered from you trying to play a song, GATT sends a wake command to the receiving device which brings it out of its low power mode and triggers the A2DP profile to start decompressing the data stream and processing the codecs to deliver your music.

A2DP hasn't changed much as a profile because it doesn't have to. It has no impact whatsoever on BLE, all of that is handled via GATT. The A2DP profile doesn't even know it's not talking to GAP since GATT fills that void. The same is true of HFP. The compression of the data stream and codec processing is all handled within subsets of the A2DP profile and the codecs are vendor specific. A2DP changes from device to device on a codec level but the Profile spec doesn't change because there's no reason to mess with it as it would cause whatever vendors device that messed with it to no longer be certified from the consortium.

Now let's get back to the core issue, Bluetooth 4.0 headphones. BLE does have power savings and some data throughput enhancements but it has to be tied to another Bluetooth 4.0 device (as the hardware requires a specific chip). The instant one or the other device isn't 4.0, everything goes down to the lowest Bluetooth version and gets rid of the benefits of 4.0. People who only use bluetooth headphones for say, a jog, aren't really going to notice the difference between 4.0 and lesser versions. However if it's someone like a power user who spends all day with a bluetooth headset in their ear and taking calls constantly, they'll definitely notice the power savings.

If you want to read the developer pdf about A2DP to learn more about how it works, go to: http://developer.bluetooth.org/TechnologyOverview/Documents/A2DP_Spec.pdf