Ten years ago, John Piper attempted to convince Bethlehem to allow for non-immersed believers to be members. The plan never succeeded. Recently the Canadian Fellowship of Evangelical Baptists discussed doing the same thing. Read about it here.
http://www.fellowship.ca/MembershipBaptism
A Baptist church that doesn’t insist on immersion is like Roman Catholicism with no pope. Roman Catholicism without the pope is . . . Anglicanism. Baptists who permit sprinkling are . . . no longer Baptists, whatever they call themselves.