The way I interpreted it is that it is going to be difficult to access such material on blogspots.
Their wording at the start of the email, "we'll no longer allow blogs that contain sexually explicit... etc." is very forthright.
Taking this introductory sentence into consideration when we look at the action they state they will take suggests that it's gonna be extremely difficult for developers on blogspot to attract new viewers.
"No content will be deleted, but only blog authors and those with whom they have expressly shared the blog will be able to see the content that we've made private."
I could be wrong, this is just my interpretation, but it seems like the adult blogs could become 'shared' like Google Docs without the 'public' option. The nightmare scenario is that you would have to enter individual emails of users that you want to see your content.
Does anyone know if this policy could negatively affect adult blogs on Google search results?