I received my notification letter from BMW NA today. It states that
...BMW is extending the limited warranty for the Supplemental Restraint System's (SRS) front passenger air bag seat occupancy sencor (OC3) mat on the above referenced vehicle to:
15 years without mileage limitation, as determined b your vehicle's original in-service date."
...
This is notice of a "limited warranty extension" only. This is not a Recall or Service Action.
Bolding is as in the original letter.
Based on the last bolded sentence, unless your SRS/Air Bag malfunction indicator is illuminated, I doubt that taking an affected car into your dealer would result in them actually doing anything, because, as stated, "This is not a notice of Recall or Service Action".