They're not leaving the Baptist as I read it. No SBC invited, but lots and lots of other Baptist, if I remember correctly.
I think they are making their own Baptist Denomination as I read it.
The SBC has a moderate-liberal group that hangs on in spite of the conservative direction of the denomination. Personally, I believe it is because the pastors of these churches have their money wrapped up in the annuity board.
But, to understand the SBC you just need to understand one thing. The Cooperative Program. That is our Missions organization. SBC member churches typically give to this program to help supply the needs of our missionaries - many of whom live daily in harms way. There are other commonalities, but really if you wonder what will distinguish the SBC from other Baptists it is the CP.
The liberals have their own missions organization called the Cooperative Baptist Fellowship. It reflects the views of its supporters.