1) Unless you want to wait for Intel Powerbooks, I doubt any major upgrades will occur until then.
I bought my Powerbook back in January and recieved it a few days before the updated ones came out. I'm actually pretty confindent my PB was one of the last 1.33 ghz 12" produced, as according to serial number info, it was made in the 3rd week of January. The new powerbook came out on Januray 31st.
Do I regret not ordering a week later? Not really. The speed bumb was small, from 1.33 ghz to 1.5 ghz. Not a big deal in my opinion. Yes, they did add that sudden motion sensor, but I regularly back up my hard drive, and if I drop my PB the last thing I'm probably going to be worried about is losing data. As for trackpad scrolling,
iscroll2 is pretty similar to Apple's built in scrolling. Concerning the added RAM, well I would have just taken the newly provided 256 MB out of the slot and added 512 MB, so that would have been useless. The price reduction would have been nice, but I was already getting a student discount in the first place, so I'm not complaining
2) My 12" PB does get pretty warm, but never enough to be uncomfortable to have on my lap. I also have a Dell laptop, and even when it's not running processor heavy programs, the bottom gets hot enough to actually burn you.
3) I'm a pretty klutzy person who often damages things, but after about 6 months my PB still doesn't have any dents or scratches on it. My secret: Keep it protected in a good case (I like the neoprone kind) when you're out, and at home just be careful around it. Oh, and be selective in who's allowed to play around on it. When little cousins and such come over, I just guide them away from the PB and over to the Dell
4) So far after 6 months, my PB hasn't even come close to getting old. Even now, I'm still finding new little things on it I never knew existed. For example, I just realized the other day that I could put a cool little character palette in the top menu bar, through the international section of system prefs. Now it's a whole lot easier to find symbols and accented words. You have no idea how much easier this makes my Spanish homework! Besides, I've seen people on these forums who have had Powerbooks for 4 or 5 years and still find them useful.