I think F1 will never come back to NA engines because the hybrid technology is the future and the money invested in R&D in this field are useful for their automotive business. Back with NA engines the costs will surely be capped because the field of engine developement would be narrower than today with a more focus on the aerodynamics, but invest a lot of money just to design new and new wings, winglets, nolders and fins is somenthing that cars manufacturers are not interested to.
Also, if F1 leaves the hybrid technology then the LMP1 cars would remain alone as the more techological advanced race cars, not very good for F1 prestige.
Also, if F1 leaves the hybrid technology then the LMP1 cars would remain alone as the more techological advanced race cars, not very good for F1 prestige.