Mann+Hummel claims these plastic housings reduce weight and help with emissions. BimmerBoost is not sure what the emissions benefit to the plastic housing actually is. The main difference is seemingly in the weight loss which then reduces the energy requirements to move the car. It's obvious why BMW would want this technology researched as the plastic material would help save weight and also likely costs as a plastic turbo will be cheaper than a high grade metal unit.
With BMW going for efficiency above all else we may start seeing plastic turbos at least in the economy models. It is doubtful a plastic housing would hold up to the rigors of a turbo M motor and then questions are raised as to how the material would fare under high heat conditions in a racetrack setting.
Head of development at Mann+Hummel Dr. Huurdeman had this to say, "The practices we have implemented successfully over the years for many plastic engine components were much harder to implement when replacing aluminium with thermoplastic PPS (polyphenylene sulphide) for turbocharger compressor housings. For example, the dynamic pressure loads at high compressor outlet temperatures entail very particular construction and material requirements."
If the plastic housing is able to deliver the durability and reliability BMW desires for a certain power level it will be no surprise to see it implemented. Plastic turbos coming soon? Sure looks like it.