When we were at Palo, they recommended upgrading to any bottle of wine on the wine list there, just pay the difference from what the wine on the package is worth.
Also one more note on how flexible they were with the package....We purchased the wine package on the first of two cruises done back to back and they allowed us to transfer the two bottles we had left from cruise 1 to the second. Our head waiter (who was the same for both cruises) just notified our waiters on #2 (not the same) that we had two bottles remaining and they brought them to us at our request at dinner, no problems.
If you enjoy wine, it is the way to go!