I believe it was first tabled in 2013 - they knew it was coming. Regardless, having multiple brands (and specialized models) under one corporation competing against itself and outside companies is just f*cking stupid. The fact that GM is just waking up to global platforms now is pathetic. As is any dink who clamors for brand loyalty and threatens to walk away from GM, Ford, whoever for some antiquated logic. Build what sells, and forget the rest. Either your product/business is solvent or it isn't. People don't matter, the bottom line and shareholders do. Keep in mind the numerous (recent) instances of corporate collaboration in a spectrum of initiatives from transmissions to full blown cars.
It's just business.