The problem is that timbthumb.php is usually contained within themes or plugins. There's quite a few small php libraries with little insecurities dotted all around the web and sometimes theme and plugin developers tend to use a version and stick with it.
Realistically the best thing that could happen is that plugins like WP-Security Scan could check for timbthumb.php's presence and warn you.
Realistically the best thing that could happen is that plugins like WP-Security Scan could check for timbthumb.php's presence and warn you.