Add a "coming soon" to main doc page (#1501)

* wip

* address review comments

Author: markxnelson

docs-source/content/_index.md

@@ -17,8 +17,35 @@ Oracle is finding ways for organizations using WebLogic Server to run important
 The fastest way to experience the operator is to follow the [Quick Start guide]({{< relref "/quickstart/_index.md" >}}), or you can peruse our [documentation]({{< relref "/userguide/_index.md" >}}), read our [blogs](https://blogs.oracle.com/weblogicserver/how-to-weblogic-server-on-kubernetes), or try out the [samples]({{< relref "/samples/_index.md" >}}).
 
 ***
+##### Current release
+
 The [current release of the operator](https://github.com/oracle/weblogic-kubernetes-operator/releases) is 2.5.0.
 This release was published on February 26, 2020.
+
+##### Preview of next planned release
+
+The next planned release is 3.0.0-rc1 (release candidate).  This release candidate will
+be suitable for use by early adopters who wish to test 3.0.0 features and provide
+feedback.  
+
+This release is planned for April 2020, subject to change.
+
+The planned feature changes in 3.0.0-rc1 are:
+
+* Introduction of a new "Model In Image" feature which allows you to have a domain
+  created at pod startup time from a WebLogic Deploy Tool model and archive.
+  This supports user-requested use cases like creating multiple domains from 
+  the same model and automated updating of the domain based on model changes.
+  The operator automates management of the domain encryption keys to ensure
+  that they are not changed during domain updates.
+* Support for running the operator on Kubernetes 1.16, 1.17 and 1.18.
+* Deprecation and removal of support for running the operator on Kubernetes 1.13
+  and earlier versions.
+* Deprecation and removal of support for Helm 2.x.  Helm 2.x uses the "tiller" pod
+  which needs to run with elevated privileges (`cluster-admin` or very close to that)
+  and which could be a vector for a privilege escalation attack.  Helm 3.x removes
+  tiller and does not create the same exposure.
+
 ***
 
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