PWRC (the former group N) is still susceptible to exotic versions if the manufacturers thought there was money to be had. They, under current regs, only need to make 2500 from a 25000+ unit production model to qualify.
Let's say Peugeot made 2500 insanely equipped £30,000+ 207's then they could enter - the only reason they don't is that the WRC is where the publicity currently is and they wouldn't recover close to the costs.
If more people (I mean those people that think a car that has a body-shape vaguely the same as won the WRC means it's a pedigree rally car) took more interest in PWRC then the mass-market companies may jump in with limited-run cars.
As group N has been around for years without this happening I think it's safe to assume only Subaru/Mitsubishi have any real interest in producing a road-going rally-capable car and that the mass-market companies believe the people watching it will remain a minority vs. the WRC.