Shame no-one answered this because I was looking for confirmation of what I was thinking on this exact scenario.
I think it will depend on how you updated the entity, whether it was attached or detached, also how you have set up caching.
However I think this would be a rare case. The business key examples given as examples above include addresses which is not a true business key. If you have any list of contacts that is more than a few items long, then you would be unlikely to use address details as part of the business key. People change their addresses all the time. In an ideal world, business key values would never need updating and if for any reason in your business domain they did need updating, you would need to design for that and not rely on Hibernate to sort out potential problems like that. And I think it's reasonable to assume that your persistence engine e.g. Hibernate would act unpredictably. I'm going to google more and if I don't edit this later, then assume I didn't find otherwise.
4 years late but better late than never....