First, I'm not a lawyer, I just have a keen personal interest in IP law, from a desire to be a well-educated consumer and creator. You likely don't need legal advice for this, but if you do, get a lawyer, &c.
Yes, the "NDA" is still in effect, but no, it doesn't control use of the retail rules.
The Online Playtest Agreement ("OPTA") only covers the material in the playtest packet. It has no relationship to any material accessed (legally) in any other way; so the retail rules have no connection to the OPTA. Being bound by the OPTA in relation to the playtest packets has no effect on your legal relationship to the retail products in question.
That said, just because the OPTA doesn't bear on your use of the retail rules doesn't mean you can freely quote them. The retail rules are still protected by copyright law, which will vary depending on the jurisdiction you live in. In general, you can expect that discussing and paraphrasing the rules is fine, but copy-pasting them (or copying-then-editing-into-different-words) is going to be a violation of copyright unless that copying falls under a "fair use" or similar exception provided by your local copyright laws. In general, it is safe to assume that any copying at all is not permitted under your local laws; it's often also safe to assume that a violation is unlikely to result in anything more than a stern "remove that, and don't do it again". Again, consult a lawyer if you have any concerns about how you use text owned by Wizards of the Coast.
Finally, just because the rules are out there doesn't mean the OPTA doesn't still control the text that appears in the playtest packets. If you want to discuss a rule in a retail product that happens to also appear in the playtest packet, you still can't quote or distribute text from the playtest packet, even if copyright law wouldn't prevent that use, because the OPTA says you can't. The OPTA (and copyright law) doesn't care if text is the same elsewhere, it cares where you got the text that you are copying. The OPTA doesn't have an expiry date either, so it applies to the playtest packet text forever.