Upgrading existing vCenter is possible, Instead of moving pools across vCenter.

Please refer to http://www.vmware.com/pdf/view45_upgrade_guide.pdf

I dont think there is a easy way to migrate pools to a different vCenter in a few clicks (specifically if automated pools are defined at source vcenter server)

After upgrading the vCenter Server, new ESX servers can be added and new clusters can be defined.

Further existing pools can be edited to select new Cluster and datasore. After this, performing a rebalance will place the pool to the new resource pool/host cluster and datasore.