I think that is just the plugin that displays the download links: Currently the configured miui version is not yet finished so the plugin displays this message instead of the table with download links.
New MIUI-Releases are JB. You need to update your hboot to use those roms.
BUT: Hboot-Updates are CID-dependend, so you have to wait for your carrier to officially release a JB update to get your hboot updated.