Starting in BuddyPress 7.0.0, community administrators will be able to assign more than one member type directly from the user’s WP-Admin/Extended profile page.
The regular select box of the Member Type metabox has been replaced by a multiple select box so that you can assign as many member types as you need to a single user.
Be aware of a change we made to the Member Types bulk actions behavior.
Community Administrators can bulk assign a member type to a list of users from the corresponding Administration screen by:
- activating the corresponding checkboxes at the left of users avatars.
- selecting the Member Type name from the Member Types dropdown list that is located over or under the users table.
- clicking on the change button immediately at the right of this dropdown list.
This strictly means you are changing the existing member type(s) of a user to the selected member type. In other words, if the user nicknamed imath was selected, he would be reassigned to the Lead Developer member type only (and lose the Pizza lover one 
).
If you choose the “No Member Type” option, then all the assigned member types of the selected user(s) will be removed.
If you want to read about how this change was made and thank the contributors who made it happen, head over this trac ticket.
By the way, did you know you’ll be able to create, edit, delete Member & Group Types directly from your WordPress Administration in BuddyPress 7.0.0 ?