Imagine a Kleenex brand PC. Imagine a Toshiba bed. Imagine an Apple iCar. Does your loyalty inspire you to 'try' these unusual combinations? Are you more apt to love that new PC from Kleenex, because you like their tissues? This one is simple, and engineer-types like simple: Brand Loyalty doesn't cross product genres... Apple would have to spend a ton of money, time, and tests to get anyone to buy their new car.
The better question is, does Brand Loyalty matter at all? Is it the brand or is it the product experience that keeps you coming back for more? And if a user has a bad experience with a new product from a brand they trusted... what happens? They disdain that product... but not necessarily the one(s) the knew and loved.
Put it this way.... would an Apple iCar failure hurt iPhone sales? Would a Kleenex PC that frustrates and annoys cause a drop in Kleenex sales?
I don't think so.