Not so sure I understand why there is so much hype about the process. It has been around for many, many years. It is just that it has up until now rarely been used in such a high profile motoring application.
In the grown up world (ie not teh interwebz) plasma coatings have been used to refurbish, reinforce, strengthen, protect, modify etc etc no end of engineering components - from stuff like pump shafts to wear parts to components needing a protective stainless coating.
There is no reason to believe the coatings on the motor will be any less successful than old school cast iron. Anyway when they fail you should be able to get them redone & rebored. So no need for oversized pistons....