[IAmBen]

The question I'd be asking myself is "Do I really need the Macbook now?" I know you probably want one right now...instant gratification style, but do you need it for the work you're doing in high school? My guess is probably no, you've probably got a computer at home that will suffice over the course of the year.

I'd hold out until you head off to college. It's a year from now and trust me, you'll want to be cutting edge when you get to school. It's nice and it's going to have to last...which will be much easier when you've subtracted a year.

However...I'll go ahead and answer a few of your questions.
1. By October it will have been a while since the last Macbook update so I think you can pretty much guarantee it.
2. I would guess no on the new body simply based on Apple's notebook past. The iBook/Macbook line has always been plastic and the Powerbook/MBP line has been metal. My guess would be they'd stay with the plastic.
3. The Macbook Pro for me wasn't bothersome at all. When you're used to carrying tons of school books, the fact that a laptop is in your bag doesn't make a **** bit of difference.
4. Functionally durable, both are. Personally I think the plastic casing gives the MB a bit more functional durability. But let's be honest, you drop either of them and you're SOL.
5. Cosmetically durable? Both scratch pretty easily without a case in my opinion. But if I had to pick one I'd say the MB, for the simple fact that it's harder to tell scratches in plastic than it is on metal.
6. No idea on your backlighting questions.

I think the MB is perfect for you with 2GB of RAM which will take care of your photography needs. Personally I'd hold off on it for it now.