You can think of Graphene, aka 'The Graphene Toolkit' as "an industrial strength software platform for deploying third generation cryptographically secure decentralized ledgers known as block chains" - http://docs.bitshares.org/
The Graphene Family of blockchains include Bitshares, Steem, Muse, Peerplays. And EOS is essentially a further expansion upon this toolkit.
Steem and Bitshares could both decide to migrate to EOS in the future... it will be up to the respective communities to decide what's best for them. For now, EOS is still in development, so I expect Bitshares and Steem to be quite relevant, and independent, for quite a while.
Ok thanks for the info. I just havent had time to read indepth into the tech. Will try to touch on it later on.