When Apple launched iPhone 6, 6 Plus and iPad Air 2, it was sold with Bluetooth 4.0, and now they have just changed the technical specifications on official website. Bluetooth 4.0 has been replaced with Bluetooth 4.2. Now onwards all the new iPhone 6 and 6 Plus will be available with the latest bluetooth version (4.2).
Bluetooth 4.2 is 2.5 times faster, and provides 10 times better data capacity along with improved security and privacy compared to its predecessor. Earlier, it was possible to upgrade the older bluetooth version to the newer one via firmware update. However, Bluetooth 4.2 requires new hardware, but this is not clear what Apple has done.