Remarkable that it was caught on video. Here's another instance of spotters potentially contributing to aviation safety with documentation of an incident.
Statistically it will happen. Does anyone know the probability?
Not off-hand, but ETOPS sets a maximum rate, among other requirements. I can't seem to find the allowable in flight shut down rate for ETOPS 330 in a quick search, but for ETOPS 180 it's 1 per 50,000 engine hours. I think ETOPS 330 is 1 per 100,000.
According to All Things 787, there's been 446 delivered so far. They're probably accruing well over 1 million flight-hours (2 million engine hours) per year at this point. In flight shut-downs once or twice a month across the entire in-service fleet don't sound out of the question.
But not all shut-downs are equal. An uncontained failure is significantly more hazardous, as it can potentially damage other systems. There doesn't seem to be any word yet about visible damage to the cowling in this case, so I'm assuming whatever failed was contained, and the metal parts in question were ejected out the rear of the engine. If it wasn't contained, it's not unprecedented, and would likely result in added inspection requirements until a root cause is identified and addressed.