I would have to say that since this is preliminary info many of us have no way to confirm the device's specifications, so we will have to wait for the phone's release to see all. For as long as I can remember Bluetooth, it has been regarded as a quick & easy short range convenience. It usually is used for transferring small files, so high speed is not as important as high efficiency. Most HID devices should work well, including A2DP which would include car stereos, portable speakers, and headsets. The biggest advantage to using 4.0 are improvements in the pairing mechanism, which can make transactions faster, and initial setup quicker. Second to this there are a wider variety of profiles available to make Bluetooth devices more useful, and versatile.
RC1024 all true about Bluetooth 4.0 and its advantages but you missed a major one: Low Energy. Its like you said, "...so high speed is not as important as high efficiency."
They are highly unlikely to change the plug type as Europe mandated that chargers and charging cords for phones be interchangeable so that every new phone upgrade didn't send an old charger to the dump. In order to comply with Europe's rules HTC and the other manufactures are likely to make all their phones comply. I am curious how CrApple avoids compliance.... http://www.slashgear.com/micro-usb-formally-chosen-as-cellphone-charger-standard-by-european-standar...
If you look on the phone itself it says it has Bluetooth 4.0.. Go to "Settings". Scroll to bottem of list. Click on "About". Click on "Hardware Information". Second thing up from bottom is: Bluetooth 4.0
You are correct, I did not mention low energy as a separate benefit I meant to imply in saying high efficiency. I really couldn't say much about the 4.0 standard because I'm not too familiar with it.
I'd say they likely do not have to worry about this regulation because their charger arrangement consists mostly of a wall wort with a standard USB port, and a USB cable that fits at least a half a dozen models that are very popular, beyond this I'd suppose we'll have to speculate.