Hi Dayandnightp,
Yes, it is possible.
As you mentioned, after you install the new Exchange 2010 server and deploy the high availability for the on-premise environment, we just need to re-run the Hybrid Configuration Wizard (HCW) and add the new server on the Servers page of the HCW
As a tip, to let an Exchange 2010 server as the Hybrid server for an Exchange 2003 environment, the Mailbox Server role is required. In other words, the Mailbox Server role needs to be installed on the new Exchange 2010 server.
Thanks,
Claud