I have a 2009 Gold Pass and I am planning on visiting the park on one of the four renewal days to renew my pass for next year and get the discount. But I do want to get a Platinum Pass because I have a chance to go to Cedar Point more than once next year. Is there any way I can upgrade from the Gold to the Platinum while still getting the renewal discount?

Yes. All you need do is buy a Platinum Pass. They will give you the renewal price if you have a gold or Kings Island pass.

Yes, you will get the Platinum renewal discount ($145 versus $150). But you will not get the special gold discount which is valid only on those select days, as it applies to only those renewing gold season passes, not platinum. Feel free to correct me if I`m incorrect on this.