I don't think they'll become commonplace. They cost too much. It's much cheaper to buy a scope and a rangfinder than to buy 1 unit that does both. And lets say you have lots of guns, buying a scope for each and 1 rangfinder lets you use a rangefinder with all of them. Buying the combo lets you use a rangefinder with only the guns you've bought the combo for.
The only place I can see them becoming more common is for expensive outfitted hunts. This lets someone carry only 1 piece of equipment. I'd imagine a smart hunter would have one of these on his rifle and another regular scope and rangefinder in his luggage if the combo has problems. That way he's not without a scope and rangefinder.