<?php wp_list_categories('show_count=1&title_li='); ?>

<?php
$variable = wp_list_categories('echo=0&show_count=1&title_li=<h2>Kategoriler</h2>');
$variable = preg_replace('~\((\d+)\)(?=\s*+<)~', '<span style="float:right">$1 yazi</span>', $variable);
echo $variable;
?>