update coming soon pages

units/en/_toctree.yml

@@ -38,9 +38,9 @@
 - title: "3. Use Case: Advanced MCP Development"
   sections:
   - local: unit3/introduction
-    title: Introduction
+    title: Coming Soon
 
 - title: "Bonus Units"
   sections:
   - local: unit4/introduction
-    title: Introduction
+    title: Coming Soon

units/en/unit3/introduction.mdx

@@ -1 +1,3 @@
-# Introduction 
+# Coming Soon
+
+This will be another use case that dives deeper into the MCP protocol and how to use it in more complex ways.

units/en/unit4/introduction.mdx

@@ -1 +1,5 @@
-# Advanced Topics, Security, and the Future of MCP
+# Coming Soon
+
+This unit will be a collaboration with partners from the AI community.
+
+If you're building tools for MCP, please reach out to us and we'll add you to the unit. Open a [discussion](https://huggingface.co/spaces/mcp-course/README/discussions) on the hub organization.