Clarify that closure may be later

content/proposals.md

@@ -503,21 +503,29 @@ and may require an MSC number to make that implementation easier.
 Placeholder MSCs are used to represent proposals in a state where implementation
 is ongoing, but the MSC details can't yet be disclosed. Authors which feel as
 though their MSC could be highly sensitive MUST get in contact with the Spec Core
-Team or Security Team prior to opening their MSC. If either team determines that
-a placeholder MSC is required, it may be opened as such.
+Team or [Security Team](https://matrix.org/security-disclosure-policy/) prior to
+opening their MSC. If either team determines that a placeholder MSC is required,
+it may be opened as such.
 
 There are a few expectations attached to placeholder MSCs:
 
-* They are tagged as WIP drafts ahead of receiving real content.
+* They have a title which marks them WIP, and are in the "draft" state.
+* They have the following labels: `[proposal-placeholder, action-required, needs-implementation]`.
+  * Notably, *not* `proposal`.
 * They are relatively short-lived (ideally less than 6-12 months in placeholder).
 * They propose solutions which are reasonably likely to be accepted. If a placeholder
   needs to be closed because the idea won't work, isn't needed, etc, then the MSC's
   content MUST be published ahead of that closure.
+  * Note: the MSC's publication (and therefore closure) may be delayed until an
+    appropriate point in the security disclosure cycle. For example, an alternative
+    MSC being published, or a stream of work being completed.
 * When they are updated to receive real content, the following happens:
   1. The Spec Core Team or the author leaves a comment to cause a notification
      that the MSC has been replaced with real content.
-  2. The `proposal` label (or its equivalent) is removed and re-applied to trigger
-     chat notifications in the public Matrix rooms.
+  2. The `proposal` label (or its equivalent) is added to trigger chat notifications
+     in the public Matrix rooms. The `proposal-placeholder` and `action-required`
+     labels should be removed at this stage as well. Other labels are removed/applied
+     per normal process.
 * The Spec Core Team is aware of the intended MSC's title and purpose. This is
   especially important if the Security Team approved the use of a placeholder MSC.