The good news: When you get an annual pass, you're given a voucher, and the pass doesn't become active until you hand in that voucher at Disneyworld and get your actual pass. What's more, if you were to buy your pass now, it would still be valid in May of 2006. Prices seem to only go up at the beginning of the year, though, so you don't necessarily need to buy your AP right this second.
Now the (potentially) bad news: Handing in that voucher is, techincally, the ONLY way you can get your AP validated. And the voucher itself is generic. That means your name isn't printed on it, and there's no way to prove it's yours. Which means, if you lose it, you are suh-cuh-rewed. If/when you do get it, make sure you keep it in a safe place where nothing can happen to it, and then make sure you bring it with you when you go.
Now, as far as AP hotel room rates go, I doubt they'd do away with the discount no matter how good the economy gets, as speck76 suggests. WDW knows that discount is the one main reason a lot of people get the AP. They might reduce the rate, but not get rid of them entirely. But they do limit the amount of rooms eligible for the rate in every hotel at any given time. It's a possibility that, the busier the time of year it is to go, the harder it might get to gets a discounted room. I believe May isn't usually too bad, because school is still in session. The Memorial Day weekend is probably jammed, and there might be more senior class trips, but if you were to go in early May, it probably wouldn't be so bad that the hotel you want will be devoid of rooms with an AP rate. Bear in mind though, that the AP rates for any given time period are released to the public approximately 3 months in advance. THis means, if you wanted to book a room now, you wouldn't get the discounted rate, because
a: They won't know what the discount is yet, and probably wouldn't know until mid-February;
b: You don't actually have an annual pass yet.
If you tried to book a room now for next year, I guess they'd charge you the full price for what it cost to book that room at the same time of year THIS year. You'd be required to pay one night in full as a deposit, with the balance due at check-in. They'd make a note that you intend to have an AP at check-in and prepare you for one of the rooms eligible for the discount. Then when you get to WDW, you'd first get your pass validated, THEN go check-in, they'd pro-rate you for the deposit you paid at the regular room rate and then you'd pay the balance at the AP rate.
