It will not make any difference to the 11+ exam, as the bill absorbs the GS as they are.http://gsha1.web.officelive.com/Academyfreedoms.aspx
There is a clear statement in the legislation that grammar schools will retain selection and DfE has indicated that schools do not have to make any name change. Thus far, the proposals look broadly similar to those that applied to G.M schools, when there were no ballot regulations.
I think it is basically direct funding, more choice in the curriculum and probably a fervent hope of less bureaucracy. Whether it's a good idea or not remains to be seen.