I just had a very intense discussion with our concept designer about the impossibility to build any useful language selection with DPS 2015. Building different selections just doesn't cut it, as you will always have a language selection as top level collection. And as a user I would expect to set this only once.
Was there anything planned in the meantime?
In DPS Classic you could o this by filters (not there in DPS 2015) and you had custom storefronts (also not planned in DPS 2015) where you could filter by anything in the product ID ( e.g. com.adobe.testpublication.en ) and even save the language choice on the devices local storage!
So for us it is a huge step backwards. We have big clients with catalogs in multiple languages and for those projects we could use the DPS 2015, as it is now, only with very ugly workarounds. And everything I read about all those big questions is: "it isn’t near the top of the list of things we plan to tackle". Very frustrating! 
Regards,
Toni