Yea this is a big problem. Anyone currently using Platinum passes is not going to want to upgrade to Prestige+ solely based on the fact that the lower pass has more benefits at other parks (which, right now, is the only point of having a platinum pass).
I give props for Cedar Fair not mucking with their passes that are working though.... Keeping Platinum the same still keeps things simple for the most part. The only confusion I had based on Tony Clark's blog post was if the passes still included fall and winter but upon more investigation it looks like that was confusion based only on Knott's Scary Farm which isn't included.
The one thing that's kind of going unnoticed is the $60 price hike for the platinum pass. I don't think it's totally unreasonable but was more than I was expecting. I think the drink plan and possibly dining plan went up as well..... The FunPix Season Pass seems to have dropped in price from last year (I think I paid $65 last year and it's back down to $50).