Index: wp-admin/update-core.php
===================================================================
--- wp-admin/update-core.php	(revision 17165)
+++ wp-admin/update-core.php	(working copy)
@@ -74,7 +74,7 @@
 	echo '</p>';
 	if ( 'en_US' != $update->locale && ( !isset($wp_local_package) || $wp_local_package != $update->locale ) )
 	    echo '<p class="hint">'.__('This localized version contains both the translation and various other localization fixes. You can skip upgrading if you want to keep your current translation.').'</p>';
-	else if ( 'en_US' == $update->locale && get_locale() != 'en_US' ) {
+	else if ( 'en_US' == $update->locale && get_locale() != 'en_US' && 'development' != $update->response ) {
 	    echo '<p class="hint">'.sprintf( __('You are about to install WordPress %s <strong>in English (US).</strong> There is a chance this update will break your translation. You may prefer to wait for the localized version to be released.'), $update->current ).'</p>';
 	}
 	echo '</form>';