No-one knows what this means, but there is plenty of speculation that the NSA or some other agency might have put the developers under pressure. Is TrueCrypt the new Lavabit?
Discussions on reddit:
http://www.reddit.com/r/netsec/comments/26pz9b/truecrypt_development_has_ended_052814/
http://www.reddit.com/r/sysadmin/comments/26pxol/truecrypt_is_dead/
http://www.reddit.com/r/linux/comments/26qe9f/truecrypt_is_not_secure_official_sourceforge_page/
Discussions on Hacker News:
Reddit points out that the United States diff could be explained by updating their Visual Studio version. Still, this is definitely very strange. I read through all the HN comments and multiple theories make sense to me. Maybe there will be more information at some point soon.