Hahahaha this is cute.
Okay so basically the iPhone is a very businessy/PDA device these days and is really for the clientele of people over the age of 16 but more like in college and above. Your dad (or if you pay the phone bill, you) will have to shell out a two year contract with the most expensive phone company on the planet, pay an extra premium for SMS and data charges (minimum $20 if you only want 200 SMS or something like that), and if you want a 16GB iPhone it will be 500 dollars. That's quite a lot to ask for, and even if you do give 400 towards the cause he will still need to pay a lot in the long run.
And, you mentioned before in your question, there will be an update. The 3G iPhone is expected "mid-2008" and I can say that WWDC is a likely release event (along with SDK). So I would strongly advise against buying an iPhone, at least.
Now on the other hand, you can get a 16GB iPod touch for 400 dollars that has a lot of great features, probably won't see much of an update (except for it to be closer to the iPhone with a brushed back and buttons), and the touch is only going to get better with small (payed for, it seems) updates over time, but there is no premium per month to pay for wi-fi. Plus if you know anything at all about VoIP, you could use that technology to still make some phone calls on an iTouch (provided you have a wi-fi connection). To put it short, to buy an iPod touch now isn't a bad idea, but a phone is a terrible idea.