The official Microsoft Live Search representative at WebmasterWorld said that Microsoft will finally be supporting Sitemaps (for real this time) now. Microsoft will currently support autodiscovery of your sitemap file if it is included within your robots.txt file.
Google, Yahoo and Ask.com all allow you to ping them with the Sitemaps file. Google and Yahoo have Webmaster consoles giving you a way to submit your Sitemap for upload. However, Microsoft, to this day, has nothing, but their word that they will or are supporting it.
Yesterday, Microsoft said that they have "started considering sitemaps in robots.txt and will extend this to most sites within the next few months." Meaning, they are experimenting locating Sitemaps files if they are included in your robots.txt file. But finally, they have admitted that they do not and have not offered "the ability to publish sitemaps via ping or webmaster tools." In addition, they said, they "do not necessarily take into account sitemaps listed in robots.txt files right at this moment."
When will we see Microsoft supporting the Sitemaps protocol they so happily said they would?
As of yesterday, Microsoft will use "autodiscovery for sitemaps through your robots.txt."
Forum discussion at WebmasterWorld.