Welcome to cruise-chat.
The short answer is - yes, you are looking at a possible problem. You can make this flight but you'll need everything to flow at optimum levels. You'll need to be among the first ones off the ship and you'll need dedicated transportation. The self-debarkation usually goes first. The problem is that self-debarkation has become too popular and can sometimes end up like a traffic jam at 8am in Los Angeles. You also need to limit your luggage since self-debarkation means you are capable of carrying all your bags off the ship without assistance. Once you get off the ship you'll either need a pre-arranged car or shuttle, or take a taxi. Frankly, I've been hosed by a limo service at Port Canaveral before and ended up having to get a cab to the airport. The cab is probably the best choice because they are there and waiting for customers. It isn't cheap though. Figure $140 for the fare and tip. Depending on your airline, the rebooking fee may be less than that.
I'd personally look at rebooking the air and eating the fees. Sunday is a heavy day at MCO and I'd doubt you could find seats on a later flight if you missed yours.