After posting this thread, I found a very interesting article about this topic, from two days ago. But it's in German. Maybe you can google translate it or still get the gist of it - "Ethereum - Winter comes closer"
https://bitcoinblog.de/2017/05/30/ethereum-der-winter-naht/Answered my own question. Thanks, Bloggood.
It basically says that the transition time will be long, and mining will only end in 2021. PoS and PoW will run simultaneously for some time.
Btw, is anybody here mining ETH? I'm in contact with an investor who might want to do it on a large scale. Money is there, but we don't know much about the technical side. We would be thankful for anybody who gets in contact, can answer a couple of basic questions, etc...
The article says ETH runs in 4 phases (Frontier, Homestead, Metroplis and Serenity), each one introduced by a hardfork?? So 5 coins in the end??