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At this point, your choices are no longer limited to closing off an old blog and starting a new one, but one of several options. You can now merge two or more blogs into one, move individual posts from blog to blog, or back up the blog locally or to a different platform altogether.
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Currently the options only support importing posts from other Blogger blogs, not WordPress, Typepad, LiveJournal or any other platform, though theoretically it would be more or less trivial to configure any of those platforms to generate an Atom file for use in moving to the Blogger platform.
They’ve included detailed help to aid in the process, for more information.