Does anybody know if it is possible to upgrade a KI Gold Pass to a Maxx Pass?

Yes, it certainly is. Any Cedar Fair park will be happy to upgrade your gold pass. It would be helpful, but isn't necessary, if you have the receipt for the original amount you paid, as they will charge you the difference between what you paid and the current price for a Platinum Pass....

Ok, Thanks Interpreter.

Remember, if you don't already have free parking at the park where you upgrade, they will also refund your parking for the day of upgrading!

Remember, if you don't already have free parking at the park where you upgrade, they will also refund your parking for the day of upgrading!

So if I have a Ki pass I can go up to CP and upgrade to a maxx pass

You indeed can. In fact, I upgraded to a CP Maxx pass last summer from a Carowinds pass (long story, don't ask). But what you will get will be a Platinum Pass...maxx is no more....Platinum's better, it includes parking at all the parks (maxx did not), and it includes the waterparks, even the separately gated ones...

Thanks Interpreter, you have been a great help.

You can still upgrade even if you do not have your receipt. Your Gold Pass is scanned and it shows what was paid for it and it shows the price to upgrade to the Platinum Pass. I have upgraded them all the time with no problems. Also, you can apply the price of admission to a season pass (or P1V2 ticket). Again, the ticket is scanned and it shows what was paid and applies that to the price of a season pass (Regular or Platinum). But you have to upgrade the admission ticket the same day that you visit.

True, at Kings Island...but do ALL Cedar Fair parks have the new system, finally? Put another way, has anyone had to go to guest relations to get admitted to another Cedar Fair park with a Kings Island Platinum Pass this year?

^^So far the CF parks I've been to this year are:

CP, Geauga Lake, Dorney, MiA, Valleyfair, and Canada's Wonderland.

The only problem I've had is I suspect (but cannot confirm) that my KI Platinum Pass did not scan for parking at Canada's Wonderland, however, IF it didn't they let me in anyway without a hassle.

Everything else has worked like a dream though!