John Mueller from Google mentioned on Twitter that Google can stop getting the XML sitemap files if the URL for the Sitemap file is found to be invalid. He also said that it is okay to have URLs that redirect but the minimum requirement is that they should load content. If they do not load content, Google will start ignoring those sitemaps.
John said that Google would stop fetching the sitemap files if the URLs are found to be invalid, but if you are returning the content or opting for redirecting (which is mostly recommended), then Google will keep trying for them. It should not cause any problem because the overall sitemap files are a very minor part of all the URLs that are fetched from a particular site. You need to ensure that the sitemap URL is valid.
So make sure sitemap URL is valid.
Forum discussion at Twitter.
Update from John Mueller: