However, I would propose that Bluetooth is becoming largely irrelevant in the face of newer technologies that supplant its capabilities with more feature-rich, capable, and robust solutions. The need for a comprehensive solution stack is being greatly diminished, and increasingly will only impair new capabilities from being developed and brought to market in a timely fashion.
I think it's only a matter of time until the Bluetooth capabilities are completely supplanted by new technologies. Wi-Fi Direct provides an easy-to-use personal area networks (PAN) where its predecessor, Ad-Hoc Wi-Fi, failed. It also provides backward compatibility with all existing Wi-Fi enabled systems. Cost and battery life concerns of Wi-Fi have also largely been addressed. Apple AirPlay and AirDrop protocols provide simple solutions for audio / video streaming and file sharing (over Wi-Fi). NFC enables short-range, one-time, transaction oriented information transfer. Add to that the emergence of feature-rich mobile platforms and a robust mobile application development community, and the need for integrated protocol stacks like Bluetooth seem greatly diminished if not completely irrelevant.
Meanwhile, the Bluetooth ecosystem appears increasingly fragmented. Bluetooth 3.0 and 4.0 provided newer features, but are not backward compatible with previous generations of Bluetooth technology. Recent news also seems to indicate that Bluetooth is clinging to newer technologies in an attempt to maintain relevancy. Consider that almost all recent Bluetooth development has focused on leveraging other technologies to extend its capabilities and useful life. Bluetooth 3.0 (and later) leverages Wi-Fi for high-speed data transfer, and the Bluetooth SIG announced device pairing using NFC will soon be supported.
The one gap remaining to Bluetooth replacement will be embedded devices, such as audio peripherals, medical/fitness instrumentation, and in-car systems, that cannot easily be upgraded or replaced in the short-term. Manufacturers will slowly drop support for existing Bluetooth solutions, and opt to develop new solutions based on alternative technologies. This will leave Bluetooth hanging around for use with legacy systems for a few years, albeit with one foot in the grave.
But ultimately it appears that Bluetooth's fate has already been decided.
R.I.P. Bluetooth, you just don't know it yet.