Google Webmaster Tools has begun reporting if your Sitemap file contains too many URLs that redirect. The error will be listed as a Warning with your XML file with the following message:
URLs not followed
When we tested a sample of the URLs from your Sitemap, we found that some URLs were not accessible to Googlebot because they contained too many redirects. Please change the URLs in your Sitemap that redirect and replace them with the destination URL (the redirect target). All valid URLs will still be submitted. Help
Google’s help screen provides reasons and assistance on how to correct the errors and basically suggests that you change the URLs within your XML file to point to the destination URL instead of the redirected URL. The warning message appears to report both 301 and 302 type redirects.
Overall, keep your Sitemap / XML file up to date with the proper URLs minus any redirects. Remember, Google is watching!