I'm coming to like Brasero more than I did before (hardly used it in the past to be honest), and now I'm wondering, are the plugins that come with the default install the only available plugins? I don't remember seeing any in apt, so I guess they would have to be plugins you download, compile and install (fun fun fun :P!).
Well pending any answers to the contrary, I'm going to say it: No There aren't any out-of-tree plugins available for Brasero at the moment.
I've just had a 10 minute hunt around lead me to the solid conclusion: Brasero needs better documentation!
If you want newer plugins (I don't think any of them are new, they're just newer versions), grab the latest tar from their FTP and compile it up. I can't guarantee any form of stability. I'd say if it ain't broke, don't try to fix it.