I have spoken to numerous people from Disney and the Hyatt about transfers. Everyone I spoke to confirmed that you can purchase transfers from the Disney reps at the airport. I also spoke to a Disney manager who confirmed that we could purchase bag only transfers from the Disney reps at the airport (this will be helfpul for us because we are staying at the Hyatt the night before, and taking our own limo to PC, so we will likely purchase the bag only transfers for our big bags that don't fit in the limo. The cost is $25 for up to 6 bags). Also, we just received our documents for our upcoming cruise, and they clearly state that transfers can be purchased from the Disney reps at the airport. By the way, a Disney manager also confirmed that we cannot check our bags at the airport desks at PC unless we have Disney transfers. However, this manager said that we could purchase transfers on the ship, but had to buy transfers for everyone in our group in order to use this service ($25 per person). Bag only transfers are not available for the return trip from PC to the airport.
I'll let you know whether we find out anything new when we return. Also, I would be interested in hearing from anyone who received any recent information that differs from what I have been told.
Good luck and enjoy your trip.