Dexos is nothing more than a licence to print money. There were, and probably still oils out there that are not dexos approved yet come from the same batch that goes into the bottle with the dexos label attached, I read about it on an oil site, where they explained that they can sell the same oil cheaper because they don't add a dexos approved label on the front and therefore are not paying for that licence.
Ive noticed most companies are starting to drop Dexo's certification here in Aus.
The US brands like Mobil and Valvoline will probably keep it given their main market being the US.
For example, from comparing Penrith Dexos GF-5 to GF-S, the products are identical, but GF-S doesn't have the certification. I think same is happening with Nulon and Castrol too.
Makes sense, zero point for the companies to pay the likely big fees to GM over a dead brand, especially with the 7 year warranties set to expire from next year on for the final MY17's