I was just checking kb:
. Update Manager 5.0 is capable of upgrading ESX/ESXi 4.0 and 4.1 hosts to ESXi 5.0. Update Manager is not capable of upgrading an ESX/ESXi 4.0 host to ESX/ESXi 4.1. Update Manager 5.5 can upgrade ESX/ESXi 4.0/4.1, ESXi 5.0, and ESXi 5.1 hosts to ESXi 5.5.
Same can be true for update manager 5.5