Just a suggestion, but would it be possible for you to enter hypothetical date for the release of the film but also have a check box field for “To Be Determined”. That way, the entry will still sort in your lists but the date that you insert will be replaced with “To be determined” in the page view?
<span class="release_date">
<?php if get_field('tbd'){?>
To be determined
<?php }else{
the_field('release_date') };
?>
</span>
This might only be a duct-tape solution and there is probably a better answer to this, but it should work for the time being.
