Bitshares is the exchange for entering and exiting Steem. But also for investing / trading purposes for any extras you would/could make on Steemit., if you decide not to invest in SDM. It is an ecosystem and all can benefit from eachother. The extra important part will be the SteemGo Coin that will be floated (ICO) on the Bitshares exchange for ownership, managing, trading and growing the SteemGo community.