Wordpress - Getting Thumbnail Path rather than Image Tag

Thumbnail is essentially attachment so you can approach from that side - lookup ID with get_post_thumbnail_id() and fetch data with wp_get_attachment_image_src(), like this:

if (has_post_thumbnail()) {
    $thumb = wp_get_attachment_image_src(get_post_thumbnail_id(), 'thumbnail_name');
    echo $thumb[0]; // thumbnail url
}

(source)