Not entirely sure what you are asking here. It sounds like you want to archive a copy, have it available for reference live and then re-use the same website but replace the content with the new version.
If you have a little bit of cash you can make your life very easy by purchasing this plugin: Backup Buddy. You can press a button or two and have an archive you can move and install anywhere. It is extremely useful and has saved me tons of time moving, migrating, restoring Wordpress websites.
In your case I would probably do something like install the 2011 (old conference) on a subdomain or a subfolder and move the entire website there. Using backup buddy it will change all the URLs during migration and you'll have a complete copy in that subfolder that will work just like the original. Be sure to create a new database for it and then you can go back to your original and edit it to the new version knowing the subfolder is completely separate.
You do need to be sure that you log on to the correct version when changing so I would make sure your passwords are very different to avoid confusion.
There are other ways to create a backup and re-link all your content, but for simplicity and time I've found nothing that beats the speed or ease of the plugin (and no I'm not affiliated with them in any way).