A Google Webmasters Help thread has a webmaster worried that Google has not downloaded his XML Sitemap file in about five days. I went to check the status of my sitemap file in Google Webmaster Tools and Google has not downloaded the Sitemap file for this site in five days as well.
So I decided to panic and shut down my web site. Just kidding. I checked to see if one of my more recent articles is indexed in Google and it was. An article I wrote Friday, April 17th is indexed. So is an article I wrote minutes ago, and so will this article, within minutes.
A Sitemap file is great but it does not mean Google has not indexed your content. The Sitemap file is one way that Google may find your content, but Google typically finds your content other ways, and typically Google may find your content faster without the Sitemap file. Meaning, Google will typically find new content on your site through their normal crawl process, faster then they would when compared to the Sitemap file. That doesn't mean that the Sitemap file doesn't help, I believe it does help.
In summary, don't worry about the reporting in Google Webmaster Tools. We know it is often buggy. If your rankings drop, traffic from Google dies and your Google Webmaster Tools console shows scary signs, then you know you have issues. Otherwise, make sure to use all the tools at your disposal before worrying all that much about a delay in reporting from Google.
Forum discussion Google Webmasters Help.