Update README

Author: tleonhardt

README.md

@@ -25,10 +25,10 @@ applications. It provides a simple API which is an extension of Python's built-i
 of cmd to make your life easier and eliminates much of the boilerplate code which would be necessary
 when using cmd.
 
-> :warning: **`cmd2` `3.x` has been released and there are some significant backwards
-> incompatibilities from version `2.x`. Please see the
-> [Migration Guide](https://cmd2.readthedocs.io/en/latest/upgrades/) for tips on upgrading from
-> `cmd2` 2.x to 3.x.**
+> :warning: **`cmd2` If you are upgrading from an older version, both `3.x` and `4.x` have some
+> significant backwards incompatibilities from version `2.x`. Please see the
+> [Migration Guide](https://cmd2.readthedocs.io/en/latest/upgrades/) for tips on upgrading from and
+> older version of `cmd2` to `4.x`**
 
 ## The developers toolbox