They are not mandated, as seen by them being an option on the 2016 BMW X1. Crazy, as they are standard on all new Honda's but not on the new BMW???
You prolly saw this in one of my posts - as I've talked about it a bit in the MMI fold-down threads. The US DOT had intended to mandate them in 2015, but did not. This prompted a few manufacturers to be either ready for them (e.g. Audi) or merely make them standard (e.g. Honda) - but even for 2016 when the next round of auto approvals of the mandate were to come thru for this requirement, it did not. So - so far rear cameras are NOT yet mandated but either will be shortly (next 1 or 2 years) or most manufacturers will just simply make them so anyway...almost every car already has a screen, another $6 shouldn't matter -
I would NOT be surprised to start seeing MORE front mounted cameras too - as the price for HD cameras keeps getting cheaper and the potential benefits (of seeing what your car and you saw just before that crash or simple stupid stuff to hold yourself or others accountable for) invade the privacy of your driving space - and all the other supporting stuff (i.e. screen, SD slots, etc.) is already there.
See how the insurance industry is using "discounts" (of like $5 every few months) to have you plug in an ODBII monitor that decides for you about "safe" driving practices including accelerating and braking - even in a straight line - to make their point that your privacy is THEIR business - literally. More of this WILL come and so too cameras for their (and ostensibly yours too) benefits -