I think the blog part of Glow is based on a customised version of wordpress and will continue to exist as it is. The major glue that ties everything together is the heavily customised version of sharepoint that provides glow groups and manages all of the permissions for the other parts of Glow and that’s the bit I think they’re looking to replace.
To be honest they would have been much better purely focusing on creating a single online account and sign on mechanism that was synchronised to pupils local login.