Google's John Mueller said in a Google Hangout on Google+ last Friday that changing the URL or location of your XML sitemap has no impact on your crawling or indexing of your web site.
He said this at the 49:18 mark into the video:
Question:
Recently have changed my sitemap name from whatever / sitemap.xml to something else sitemap.xml and submitted in Search Console. Will Google reduce the indexing or crawling up my website or web pages?
Answer:
No. Changing the URL of your sitemap file is totally irrelevant for us, in the sense that we find the new sitemap file, we start processing the new sitemap file and we just use those URLs there. It's not something where you have to have a history of a sitemap URL for first things to work. So that shouldn't have any effect at all on crawling indexing and ranking.
So moving the sitemap file should not hurt or benefit your site.
Here is the video embed:
Forum discussion at Google+.
