The 4.6 release was tagged several months ago, some of those who preordered the CD have already received it.. official release date is November 1st.
Many changes have been made since 4.6 was tagged, a summary is made available on the website.. there is also a source-commits mailing list.
http://www.openbsd.org/plus.html
http://www.openbsd.org/mail.html
http://marc.info/?l=openbsd-cvs
Snapshots are based on OpenBSD -CURRENT, they are not 4.6 RELEASE.