There's no way pkgsrc would ever possibly move to github, since github is a political / business entity.But NetBSD has an account in there (I believe it's an official account). What's the point of having a presence on Github?
Your question was about pkgsrc migrating to git/github. I answered about moving to github - it'll never happen. pkgsrc will always live on NetBSD servers. We eat our own dogfood, as the saying goes.
The NetBSD Foundation and various NetBSD developers have github accounts, of course, but that's to make working with other github projects easier. This isn't related at all with moving to github.
John