docs: new roadmap process (#1607)

Author: dunglas

extra/releases.md

@@ -2,15 +2,18 @@
 
 API Platform follows the [Semantic Versioning](https://semver.org) strategy.
 
-Only 3 versions are maintained at the same time:
+3 versions are maintained at the same time:
 
-* **stable** (currently the **2.7** branch): regular bug fixes are integrated in this version
-* **old-stable** (currently **2.6** branch): security fixes are integrated in this version, regular bug fixes are **not** backported in it
+* **stable** (currently the **3.0** branch): regular bug fixes are integrated in this version
+* **old-stable** (currently **2.7** branch): [security fixes](security.md) are integrated in this version, regular bug fixes are **not** backported in it
 * **development** (**main** branch): new features target this branch
 
-Older versions (1.x, 2.0...) **are not maintained**. If you still use them, you must upgrade as soon as possible.
+Older versions (1.x, 2.6...) **are not maintained**. If you still use them, you must upgrade as soon as possible.
 
 The **old-stable** branch is merged in the **stable** branch on a regular basis to propagate [security fixes](security.md).
 The **stable** branch is merged in the **development** branch on a regular basis to propagate [security](security.md) and regular bug fixes.
 
-New versions of API Platform are released **when they are ready**, on the behalf of the API Platform Core Team.
+New major versions of API Platform are released every 2 years.
+New minor versions of API Platform are released every 6 months.
+
+The latest minor version of a major branch contains all the new features introduced in the first version of the next major, but also contains deprecated features which are removed in the next major branch.