Nope. Already own my BTR5 for almost a month now and no discoloration is detected. I reckon you can get it to turn yellow if you put it under direct sunlight or UV lamp for an hours or two every days for a week or two, but that's not what normal people will do to their BT adapter. Besides, turning yellow doesn't impact SQ, so what's the big deal there?
It will turn yellow eventually with normal use.
The big deal is the looks, ugly yellow case attached to my chest? no please.