You must upgrade by the 30th, but it can take a few days to go through, so call to do it and make sure they will use the call-in date and not the date that it actually goes through. Do NOT upgrade online. It can take 2-3 weeks to go through. Calling takes 3-5 days. As for cruise/trip/dvc payments, they will earn 5% during the first 90 days. After that, it is 2%.
ETA: The 5% back for the first 90 days is ONLY for those upgrading from the regular Disney Visa. Also, you must have had the regular card for at least one full year before you can upgrade.