Porsche and Acura plan to move to LMP1; maybe this year; I'm not sure. Frankly it was when BMW, Toyota, and Mercedes moved into F1, and Nissan went restructuring, that Audi became the only manfacturer in the top class, and started winning. LMP2 will become a true privateer's class.
They are producing a GT2-type racer so they would just need a customer over here. It would be a lot less expensive.
Edit: it's a GT3 racer; we don't have that class over here. It is a much more privateer-oriented class than even GT2.