beta drop update note

Author: kalexand-rh

updating/updating-cluster.adoc

@@ -7,6 +7,19 @@ toc::[]
 
 You can update, or upgrade, an {product-title} cluster.
 
+[IMPORTANT]
+====
+During the {product-title} beta period, update functionality is limited in the
+following ways:
+
+* You cannot update between different beta drops, such as from OpenShift 4 Beta
+Drop 2 to OpenShift 4 Beta Drop 3.
+* The ability to update from a beta drop of {product-title} to a full version of
+{product-title} is not guaranteed.
+* After you install OpenShift 4 Beta Drop 3, you can update your cluster to
+one of the available nightly builds.
+====
+
 .Prerequisites
 
 * Access to the cluster as a user with `admin` privileges.