What happens when team blogs switch to the new version of Blogger?
A team blog will only switch to the new version of Blogger when the original owner moves his or her account over.
Team members who have not yet switched to the new version will still see the blog on their dashboards, but it will be grayed out and inaccessible. Once those members move their own accounts to the new version of Blogger, they will be able to access the blog as before. If they can't yet switch, or don't wish to, they can ask the owner of the blog for a new invitation to join the blog on the new version. They can then accept that invitation by logging in to or creating a Google Account to post to that blog. (Later on, when they do switch their Blogger account to the new version, they'll have an option to merge it with this account.)
If a team member of a blog switches their account to the new version of Blogger before the blog owner does, then the team blog is not converted. It will appear on the team member's converted dashboard, but clicking on it will lead back to the old version of Blogger. Thus, the blog will still be usable, but without the new features of Blogger (e.g. Labels, Layouts, etc.).
Special case for blogs that have been moved to different accounts: In the previous version of Blogger, the team member who originally created a blog could be removed from the team. This is not possible in the new version of Blogger, where each blog must have an owner who cannot be removed. Thus, a new owner is assigned to these blogs.
Where there is only one admin member on the blog, that person becomes the new owner of the blog after they switch to the new version of Blogger. If there are multiple admins, then the last person to switch becomes the new owner. The other members will still have admin rights, but the new owner will be the permanent member and owner of the blog. So if you have a team blog that fits this description (i.e. the original creator is no longer part of the blog) you can coordinate among your members to decide who will take ownership of it.