Update upgrade guide

Author: driesvints

UPGRADE.md

@@ -4,10 +4,14 @@
 
 ### PHPUnit 8
 
-Dusk now provides support for PHPUnit 8. If you wish to make use of PHPUnit 8 the minimum requirement is PHP 7.2. Please read through the entire list of changes in [the PHPUnit 8 release announcement](https://phpunit.de/announcements/phpunit-8.html).
+Dusk now provides support for PHPUnit 8. If you wish to make use of PHPUnit 8 the minimum requirement is PHP 7.2. Please read through the entire list of changes in [the PHPUnit 8 release announcement](https://phpunit.de/announcements/phpunit-8.html). Using PHPUnit 8 will require Laravel 5.8 which will be released at the end of February 2019.
 
 You may also choose to continue to use PHPUnit 7 which requires a minimum of PHP 7.1.
 
+### Minimum Laravel version
+
+Laravel 5.7 is now the minimum supported version of the framework and you should upgrade to continue using Dusk.
+
 ### `setUp` and `tearDown` changes
 
 The `setUp` and `tearDown` methods now require the `void` return type. If you were overwriting these methods you should add it to the method signatures.