It seems to be the way that "exclusive" items become more and more accessible - and that's not unique to MINI.
With regards to the GP, there will no doubt be some owners out there who are upset by the "Inspired" model but I'm not one of them. Personally I think it's a great little car and it'll be nice for the owners who've gone for one. My enjoyment of something has never hinged on "exclusivity" - if something's great I'd always prefer that more people are able to enjoy it.
I wouldn't be surprised if MINI ended up lumping the GP engine in a regular JCW hatch at some stage. The N18 from the GP2 was used in other MINI models and the uprated B48 from the GP is already being used in the Clubman and Countryman 300 (and of course a range of BMW models). Again, this wouldn't upset me as it would just give more MINI owners a chance to experience (what's shaping up to be) a great engine.