Yes. very much possible.
You need to enable the option to check in packages into any branch of the ePO repository for deployment. Refer to the McAfee KB52901 for details on how to do this.
Once the above step is done, you would be presented with the option to check-in the Agent package into a branch other than current (Evaluation branch).
To deploy the agent using 'Deploy Agent' option, you can choose from the branch drop down based on your need.
Similarly you can configure the Deployment task to use the appropriate branch for upgrade.
What the previous tech added is probably the best way to "manage" the release of the agents in your environment.
Don't forget that there are also various reports (Example: MA: Agent Verisons Summary) available in the ePO 4.x server versions to let you know what versions your computers are currently at since the last time those communicated back with the ePO server that should help in staging agent upgrades within your environment.
Hope this helps!
Awesome - didn't know you could do this!
I'm in the same situation and just wondering if I should check in the extension for MA 4.5 or my current MA 4.0 extensions is just fine?
If you are intending to deploy MA 4.5 clients then you will need to check-in the MA 4.5 extension. The MA 4.5 extension will upgrade the existing extension for MA 4.0 and it can be used to manage both versions of the agent.