Google's John Mueller said in an #AskGoogleWebmasters video that now that "you no longer need to do anything special for hashbang URLs," if you still have those old URLs for the old AJAX crawling scheme, you should redirect those URLs.
John said you would need to use JavaScript redirects for those URLs and when you do and Google tries to access those old URLs, Google will reprocess it and find the new URL for your JavaScript or AJAX pages.
Google has been telling people to stop using the old AJAX crawling scheme for years and if you still have some legacy URLs out there, here is your solution.
John said "In short, for Google you no longer need to do anything special for hashbang URLs. We will just try to render them directly. In order to move to a different URL structure you need to use JavaScript on these pages to create the redirects. It's not possible to use server-side redirects since everything after a hash, so the number symbol, is not sent to the server but rather processed in the browser. Once you've setup those redirects, as Googlebot reprocesses the hashbang URLs on the site, it'll spot the redirect and follow it appropriately. "
Here is the video:
Forum discussion at Twitter.
