This repeating noise almost like every full tire rotation repeating and accelerating at higher vehicle speeds.
My local BMW shop is suggesting differential is the culprit, this is definitely the expensive option.
So it does not appear to be rear tires and/or wheel bearings.
What is your expert opinion on this?
I have 2 videos 10-15 sec long, what is the best way to upload the sound here?

 

Just post the links to the videos

 

Attaching 2 mp3 clips, hope this works.
One is at lower speeds and the other is at around 60 mph

 

There is a device that is very handy trying to figure this stuff out. One brand is called a Wireless Chassis Ear. If you have ever used a mechanics stethoscope to locate a noise, it is the same principle, expect it connects to a wireless transmitter that can be head on a receiver box in the car. This is handy for stuff that happens while the car is in motion. I got one used and cheap off eBay years ago and it has helped a couple times narrow down a noise only heard while driving. I would expect some repair shops to have these as well.

 

How long has it been happening?

 

That sounds like the wheel bearing to me at its beginning stage of failure.

 

I was also thinking wheel bearing first, then tire / wheel.

 

Wheel bearings will normally change the sound they're making when you negotiate a sweeping turn (try both right and left turns). This is because the forces on the bearings change, which loads or unloads the damaged portion.

 

Started hearing about 1 year ago but noticing that it is slightly louder now with more miles driven.
At highway speeds noticing that is slightly louder when taking right turns, there is absolutely no play on rear wheels when checked on lift, could that still be wheel bearing?

 

Yes.

Get an indy BWM mechanic to verify just to be sure.