With recent releases, ITMS 8.6 & 8.7, we still support earlier 2000, 2003, and 2008 domains during our Microsoft Active Directory Imports:
For IT Management Suite (ITMS), it's just an LDAP protocol that domain structure should support, so AD Import works fine. Unless Microsoft introduces breaking changes in LDAP protocol in AD, we are not concerned about the versions of AD.
Changes haven't been made in the ITMS code in years because Microsoft shipped a new version of AD import.