I just hung up with a CM.
Any days added to a ticket will be done at the current prices.
Any upgrades to current APs also will be done according to current prices, no exceptions. Even if, say, you were planning on being at the park next week to upgrade your pass to a Deluxe so you could visit the parks during the summer.
After talking to my husband, we decided its worth it to us to upgrade, even at the new prices. It's just really sad that with the economy being where it is right now, some people really can't absorb this kind of increase. I guess I hope it helps with crowds and prevents instances of full blown chaos (One More Disney Day, anyone?) in the future. Ultimately, this has just made me feel a little disenchanted with Disney and I don't know what to do with that. I don't think there is anyway to be "heard" by people that make these decisions and judging from the CM I just spoke with, they could care less.