As a rule, published blueprints are upgraded as published blueprints.
However, there are exceptions to that rule. Multi-machine blueprints are upgraded as composite blueprints that contain blueprint components. Multi-machine blueprints that contain unsupported settings are upgraded as unpublished.
For related information, see Upgrade and vApp Blueprints, vCloud Endpoints, and vCloud Reservations and Understanding How Multi-Machine Blueprints Are Upgraded.