I was told this on themeforrest by the author of X-Store
” We would recommend you to create staging site (full copy of the production). After that contact us using ThemeForest author contact form or submit topic on the support forum https://www.8theme.com/forums/xstore-wordpress-support-forum/ and provide us with the WP Dashboard and FTP access to your staging site.”
I have created the duplicate staging site and it can be upgraded to latest version of x-store. I put ftp login details in the private content area of this post