How about doing a public beta for a month or two, with a warning that afterwards everything posted on the new server will be deleted (including new user accounts, etc.), data from old server will be imported, the old server will become read-only, and the new server will become the official one.
How about doing a public beta for a month or two, with a warning that afterwards everything posted on the new server will be deleted (including new user accounts, etc.), data from old server will be imported, the old server will become read-only, and the new server will become the official one.