XML Sitemap was a very popular module for D6 and D7 sites, however, users are reporting by November 2015 that the last 8.x dev released in July 2015 doesn't work with the official D8 release. Maintainer Dave Reid is seeking a co-maintainer for this project and marked the issue as "Needs Review" on November 20, 2015.
Simple XML Sitemap is an alternate module with a streamlined code base that is currently maintained and works with D8. On November 22, 2015, the maintainer of Simple XML Sitemap, gbyte.co, noted that although Simple XML Sitemap is sufficient for some D8 sites and "in many cases more performant" than XML Sitemap, it would be beneficial for someone to continue to work on a D8 version of XML Sitemap for use cases that require more complex functionality.
# Project URL
# Where is the code?
# Estimated completion date
# Who's doing the port?
Dave Reid who is seeking a co-maintainer.