I think you're spot on in your speculation here. I don't know about the timeframe because I think the first manufacturer will meet heavier resistance, and then the 2nd company to do it will be successful, but no doubt it will happen.
I don't think R&D costs will significantly increase until after the next major price category is created. I think with regular (as opposed to over-) molds, the expensive component will be the discovery of a better polymer. Dunipace believes that the biggest thing missing from the overall current disc lineup is truly accurate high speed drivers...so maybe (and obviously I'm speculating heavily here) a yet-to-be-discovered polymer will react in such a way that solves that problem...or maybe lasts longer AND provides better grip, etc.
I would not be surprised to see changes in the fundamental changes in the way discs are manufactured eventually, and that will require significant investment, but I think there's still room to grow with the current injection molding processes.