T5 Page Template Column. Shows the page templates as separate, sortable column.

t5-page-template-column.php

<?php
/**
 * Plugin Name: T5 Page Template Column
 * Plugin URI:  https://gist.github.com/toscho/f657e323a60f12ad9605
 * Description: Shows the page templates as separate, sortable column.
 * Version:     2015.02.14
 * Required:    4.0
 * Author:      Thomas Scholz <info@toscho.de>
 * Author URI:  http://toscho.de
 * License:     MIT
 * License URI: http://www.opensource.org/licenses/mit-license.php
 */


if ( ! is_admin() || empty ( $_GET[ 'post_type' ] ) || 'page' !== $_GET[ 'post_type' ] )
	return;

class T5_Page_Template_Column {

	private $column = 'page_template';

	private $meta_key = '_wp_page_template';

	public function setup() {

		add_filter(
			'manage_page_posts_columns',
			array( $this, 'add_header' )
		);
		add_filter(
			'manage_edit-page_sortable_columns',
			array( $this, 'add_sortable_column' )
		);
		add_filter(
			'manage_page_posts_custom_column',
			array( $this, 'render' ),
			10,
			2
		);

		add_action(
			'pre_get_posts',
			array( $this, 'filter_pre_get_posts' )
		);

		// You can change or remove hooks from this class here.
		do_action( 't5_page_template_column_setup', $this );
	}

	public function filter_pre_get_posts( WP_Query $wp_query ) {

		if ( 'template' === $wp_query->get( 'orderby' ) ) {
			$wp_query->set( 'meta_key', $this->meta_key );
			$wp_query->set( 'orderby', 'meta_value' );
		}

		if ( ! empty ( $_GET[ 'template' ] ) ) {
			$wp_query->set( 'meta_key', $this->meta_key );
			$wp_query->set( 'meta_value', $_GET[ 'template' ] );
		}
	}

	public function add_header( $columns ) {
		$columns[ $this->column ] = 'Template';
		return $columns;
	}

	public function add_sortable_column( $columns ) {
		$columns[ $this->column ] = 'template';
		return $columns;
	}

	public function render( $column, $post_id ) {

		if ( $column !== $this->column )
			return;

		// $template is the path to the template file relative to the theme root.
		$template = get_post_meta( $post_id, $this->meta_key, TRUE );
		$name     = $this->get_template_name( $post_id, $template );
		$url      = $this->get_selection_url( $template );

		print "<a href='$url'>$name</a>";

		if ( 'default' !== $template ) {
			$template = esc_html( $template );
			print "<br><code>$template</code>";
		}
	}

	private function get_template_name( $post_id, $template ) {

		if ( 'default' === $template )
			return __( 'Default Template' );

		$post          = get_post( $post_id );
		$all_templates = get_page_templates( $post );
		$template      = esc_html( $template );
		$name          = array_search( $template, $all_templates );

		if ( $name )
			return esc_html( $name );

		return esc_html__( 'Default Template' );
	}

	private function get_selection_url( $template ) {

		return add_query_arg( 'template', $template );
	}
}

$t5_ptc = new T5_Page_Template_Column;
add_action( 'load-edit.php', array( $t5_ptc, 'setup' ) );