Dan's working over at EOS now. Extending blockchain functionality at block.one. From what I see of EOS code it's abstracted instances of blockchain smart contracts will be very useful for devs like me. But I don't think Dan going to EOS will impact Steem at all really, it's already gone beyond critical mass in terms of adoption and is one of the worlds first Decentralized, Autonomous Co-Operative or DACs, a term coined by Dan himself. Dan leaving the top of the mountain after the avalanche has already started, doesn't seem to me to be a big deal :)
So IMHO maybe don't sell your steem holdings quite yet. If you like game of thrones then just think Hodl ;)