Hi, Devon!
Not to worry!
There is a very informative post on Disney Parks Blog which details the latest information about the new
Disney Parks Disability Access Service Card, which is effective as of October 9th, 2013.
While the Service is a bit different than the Guest Assistance Card, I'm sure you'll be pleased to know that you can still have accommodations made which suit your son's needs. Take a look at the Fact Sheet in the link above to get a basic understanding of how the Service works. Note, too, that the Frequently Asked Questions also states that Disney "will continue to work individually with guests with disabilities to provide assistance that is responsive to their unique circumstances. Guests should visit Guest Relations to discuss their individual needs."
In short? Don't worry. You and your little prince will still be able to enjoy Disney through the use of the DAS and other assistance, if needed, from a Cast Member at Guest Relations.
Send more questions as you think of them, Devon; we love to help!