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For the XOOPS 2.x development, we're following the lInux Kernel versioning scheme, which means that the odd release versions (2.1, 2.3 etc.) are the alpha/beta/development releases, and the even releases (2.2, 2.4 etc.) releases are the stable releases which are usable for public websites and production environments. So, wait for 2.2, as that's what it's for. All earlier releases are for development and testing only.
Waiting for XooSphere to upgrade your site? Wow.. that means you'll be waiting for about a year before you can. Read the planning in the Roadmap.
Use XOOPS 2.2 (and 2.4 if that will happen).
Herko