Gandi VPS for moving site from shared to dedicated hosting

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http://serverfault.com – I have a site with reasonably high traffic that I expect to increase over time which is currently on shared hosting. My plan is to move the site (which runs on WordPress) to a Gandi VPS. Can I develop the new site on the VPS using just the IP of the server and then, when it's ready to go live, can I just point my domain away from the shared hosting and towards my VPS with the new site? The idea being that visitors to the site will not experience any downtime and the transfer should be seamless. I have never used or run a dedicated hosting plan before so would be keen to know how difficult i (HowTos)