I have booked 2 rooms on the Majic for next May. We used the early saver program. I could not find any discount for Past Guests. I am not sure how the upgrading works. We have been on 7 other cruises and we only upgraded once.
The only way to get free upgrades is if the price on a category above yours drops, you can request to be moved to that category.
You cant combine rates, so if you wanted to book past guest, you couldnt book early saver. If the past guest rate drops below what you paid, then you can price match to that rate.
ES has no built in upgrades, and you must choose your cabin, so you cant price match to any rate that is gtys like sometimes a senor rate will pop up that is a gty, or a pack n go rate. I think Carnival does it on purpose so you cant price match from ES.
Carnival does do upsells .. buyer beware, as sometimes these are decent deals, sometimes they call you and if you know prices its not a discount. They might send out emails, $40 to upgrade to a higher deck, same inside or same OV .. or it might be to upgrade from inside to OV.
Did you book specific cabins or a guarantee? I think, but may not be true, that you have a better chance is you book a guarantee catagory rather than a specific cabin. Although, I've booked guarantees before and always got the catagory that I booked, no upgrades. You have a much better chance of getting an upgrade by checking the prices and just paying a few dollars more for a better cabin.
Oh I totally agree with you Flowers, wish you could book that way. One reason I like to book a guarantee catagory, is the suprise of finding out your cabin and if it is a higher up catagory, so far, no, but you never know in the future...