There are no major changes for 2013. The ones you're referring to are proposed changes for 2014 onward. See this thread for clarification:
viewtopic.php?f=52&t=12091The proposed rules won't affect SP/SM classes either. Where SP references 13.3, it adds "Tires must meet the eligibility requirements for Street Category with the exception of 13.3.A.1, 13.3.A.2, and 13.3.A.3." which removes the treadwear and tread depth requirements.
There are no changes to the SM rules, so I presume it just keeps clause 16.1.J, "Tires legal in Stock, Street Touring, or Street Prepared are permitted."
Non-DOT slicks have never been legal below prepared class (at least not in 2012/13). DOT approved tires are what people should be using.
I'm basing all this off the 2013 SCCA/ASN rulebook and the April 2013 SCCA fasttrack bulletin.