I would change the internal URLs to the new form as soon as possible. There is a theory that Google may stop displaying the new URLs in the SERPs and revert back to the old form, if the spider detects that the preferred link is to the old format. The example that I saw was for xbox.com. The actual web site is something like xbox.microsoft.com, but xbox.com is redirected to that url. When you do a search on Google, the xbox.com form shows up in the results because a) its cleaner. It is shorter, and in most cases closer to the entered search term, and the engine is set up with certain biases to cause some URLs to be used instead of others. b) It is preferred - most web links go to xbox.com, not the page that it redirects to. As a result, the search engines guesses that that is what should be displayed in the SERPs.

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