Index: wp-admin/includes/plugin.php
===================================================================
--- wp-admin/includes/plugin.php	(revision 7430)
+++ wp-admin/includes/plugin.php	(working copy)
@@ -31,7 +31,7 @@
 	return array('Name' => $name, 'Title' => $plugin, 'Description' => $description, 'Author' => $author, 'Version' => $version);
 }
 
-function get_plugins() {
+function get_plugins($plugin_folder = '') {
 	global $wp_plugins;
 
 	if ( isset( $wp_plugins ) ) {
@@ -40,6 +40,8 @@
 
 	$wp_plugins = array ();
 	$plugin_root = ABSPATH . PLUGINDIR;
+	if( !empty($plugin_folder) )
+		$plugin_root .= $plugin_folder;
 
 	// Files in wp-content/plugins directory
 	$plugins_dir = @ opendir( $plugin_root);
@@ -109,7 +111,7 @@
 		return null;
 }
 
-function deactivate_plugins($plugins) {
+function deactivate_plugins($plugins, $silent= false) {
 	$current = get_option('active_plugins');
 
 	if ( !is_array($plugins) )
@@ -120,7 +122,8 @@
 		if( false === $item)
 			continue;
 		array_splice($current, $item, 1 ); // Array-fu!
-		do_action('deactivate_' . trim( $plugin ));
+		if ( ! $silent )
+			do_action('deactivate_' . trim( $plugin ));
 	}
 
 	update_option('active_plugins', $current);
Index: wp-admin/includes/update.php
===================================================================
--- wp-admin/includes/update.php	(revision 7430)
+++ wp-admin/includes/update.php	(working copy)
@@ -191,6 +191,10 @@
 	// Once installed, delete the package
 	unlink($file);
 
+	//Deactivate the plugin
+	apply_filters('deactivate_plugin', __('Deactivating the plugin'));
+	deactivate_plugins($plugin, true);
+
 	// Remove the existing plugin.
 	apply_filters('update_feedback', __('Removing the old version of the plugin'));
 	$plugin_dir = dirname($base . PLUGINDIR . "/$plugin");
@@ -219,6 +223,13 @@
 
 	// Force refresh of plugin update information
 	delete_option('update_plugins');
+	
+	//Return the new plugin file.
+	if( ! preg_match('!/([a-z0-9\-]+)/?$!i', $working_dir, $mat) )
+		return false;
+	$plugin = get_plugins('/' . $mat[1]); //Pass it with a leading slash
+	$list = array_keys($plugin);
+	return $mat[1] . '/' . $list[0]; //Pass it without a leading slash.
 }
 
 ?>
\ No newline at end of file
Index: wp-admin/update.php
===================================================================
--- wp-admin/update.php	(revision 7430)
+++ wp-admin/update.php	(working copy)
@@ -82,7 +82,7 @@
 		else 
 			$message = $message->get_error_message();
 	}
-	echo "<p>$message</p>";
+	echo "<p>$message</p>\n";
 }
 
 function do_plugin_upgrade($plugin) {
@@ -91,12 +91,12 @@
 	$url = wp_nonce_url("update.php?action=upgrade-plugin&plugin=$plugin", "upgrade-plugin_$plugin");
 	if ( false === ($credentials = request_filesystem_credentials($url)) )
 		return;
-		
+
 	if( ! WP_Filesystem($credentials) ){
 		request_filesystem_credentials($url, '', true); //Failed to connect, Error and request again
 		return;
 	}
-		
+
 	echo '<div class="wrap">';
 	echo '<h2>' . __('Upgrade Plugin') . '</h2>';
 	if ( $wp_filesystem->errors->get_error_code() ) {
@@ -106,18 +106,26 @@
 		return;
 	}
 
+	//Todo: is_plugin_active() wrapper?
+	$was_activated = in_array($plugin, get_option('active_plugins'));
+
 	$result = wp_update_plugin($plugin, 'show_message');
 
-	if ( is_wp_error($result) )
+	if ( is_wp_error($result) ){
 		show_message($result);
-	else
-		echo __('Plugin upgraded successfully');
+	} else {
+		//Result is the new plugin file relative to PLUGINDIR
+		show_message(__('Plugin upgraded successfully'));	
+		if( $result && $was_activated ){
+			show_message(__('Attempting reactivation of the plugin'));
+			echo '<iframe style="border:0" width="100%" height="170px" src="' . wp_nonce_url('update.php?action=activate-plugin&plugin=' . $result, 'activate-plugin_' . $result) .'"></iframe>';
+		}
+	}
 	echo '</div>';
 }
 
 if ( isset($_GET['action']) ) {
-	if ( isset($_GET['plugin']) )
-		$plugin = trim($_GET['plugin']);
+	$plugin = isset($_GET['plugin']) ? trim($_GET['plugin']) : '';
 
 	if ( 'upgrade-plugin' == $_GET['action'] ) {
 		check_admin_referer('upgrade-plugin_' . $plugin);
@@ -126,6 +134,36 @@
 		require_once('admin-header.php');
 		do_plugin_upgrade($plugin);
 		include('admin-footer.php');
+	} elseif ('activate-plugin' == $_GET['action'] ) {
+		check_admin_referer('activate-plugin_' . $plugin);
+		if( ! isset($_GET['failure']) && ! isset($_GET['success']) ) {
+			wp_redirect( 'update.php?action=activate-plugin&failure=true&plugin=' . $plugin . '&_wpnonce=' . $_GET['_wpnonce'] ); 
+			activate_plugin($plugin);
+			wp_redirect( 'update.php?action=activate-plugin&success=true&plugin=' . $plugin . '&_wpnonce=' . $_GET['_wpnonce'] ); 
+			die();
+		}
+			?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" <?php do_action('admin_xml_ns'); ?> <?php language_attributes(); ?>>
+<head>
+<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php echo get_option('blog_charset'); ?>" />
+<title><?php bloginfo('name') ?> &rsaquo; <?php _e('Plugin Reactivation'); ?> &#8212; <?php _e('WordPress'); ?></title>
+<?php
+wp_admin_css( 'css/global' );
+wp_admin_css( 'css/colors' );
+?>
+</head>
+<body>
+<?php
+		if( isset($_GET['success']) )
+			echo '<p>' . __('Plugin reactivated successfully.') . '</p>';
+
+		if( isset($_GET['failure']) ){
+			echo '<p>' . __('Plugin failed to reactivate due to a fatal error.') . '</p>';
+			error_reporting( E_ALL ^ E_NOTICE );
+			@ini_set('display_errors', true); //Ensure that Fatal errors are displayed.
+			include(ABSPATH . PLUGINDIR . '/' . $plugin);
+		}
+		echo "</body></html>";
 	}
 }