This question comes up regularly and from responses on other threads you would have a better chance of having the penalty waived if you call the dining line or speak with the concierge at your resort where it will be evaluated on a case by case basis. There is no blanket policy regarding changing a reservation at the last minute, but if you cancel online and make a new reservation at a different restaurant or a different time the system won't know why you cancelled the original reservation so you would be assessed the $10 per person penalty. You'll need to speak with a person, but even then there's still no guarantee the fee would be waived.
With CRT or the dinner shows I would not take the chance because the penalty is the full pre-payment amount and not just $10 per person. It would be better to keep checking online multiple times a day to see if something earlier opens up and if nothing comes up, make a decision before the CRT cancellation deadline comes up.
Here's a recent thread on the same subject:
http://www.disboards.com/showthread.php?t=3281503