Personally I don't want a piston driven rifle. It solves one problem and creates worse problems. That being said I wouldn't buy another plastic pistol either but that doesn't mean there isn't a market for them. They could carve out a niche with a piston rifle.
I think if they made a spec rifle (piston or GI) with the quality Colt is known for, at a competitive price, they would have a winner.
I have no idea what problems you imagine are inherent in piston driven ARs, but I have built several and have found two that run flawlessly, the Osprey Defense and then the Adams Arms. I prefer the Osprey because it is so trouble free. But the dialability for pressure of the Adams Arms version is good, too. I would guess that around 10 to 20 thousand rounds I may need to replace the drive rod ont he Osprey, but running cool in the bolt and such attributes makes it well worth it.