Add these two where you want them to display within your single.php file. It will make the title of the post a link.
<?php previous_post_link(); ?>
<?php next_post_link(); ?>
EDIT:
Sorry I missed the second part of your question about future posts. Here’s what I would probably do. It’s not tested, but will give you an idea.
$adjacent_post = get_adjacent_post(false,'',false) ;
if (get_post_status( $adjacent_post->ID ) == 'publish'){
echo '<?php next_post_link(); ?>';
}
else {
echo get_the_title($adjacent_post->ID).' | '. $adjacent_post->post_date;
}