I am very grateful that Dan Larimer will be fully dedicated to the EOS project. So, in my opinion, he did not really quit on bitshares and steemit because EOS will be their next OS. Few people on earth have Dan's talents and blockchain experience. Steemit and bitshares teams are perfectly able to take care of these platforms. The usual rule set for engineers (don't quit a project until it's finished) has to be put in perspective. Dan has been on the same project for more than a decade: making blockchain technology available to all of us !