If you thought that when iPhone OS 4.0 gets released and you can buy the 2GB "Datapro" plan for $25, along with an additional $20 per month to tether your iPhone's WiFi connection to your iPad, think again. It's just not going to happen. This is consistent with Steve Jobs' answer to an email asking him about this possibility. His response was a terse "no."
According to Apple, once enabled, you will be able to tether your iPhone to a PC or Mac either via
WiFi, Bluetooth, or a USB cable, but they didn't make mention of the iPad. It turns out that WiFi isn't possible on the tablet: the required Bluetooth profile isn't enabled, and using the camera connection kit to connect to a mini-USB port on your camera won't work either, although it will work with a USB keyboard and headset.
Not allowing iPhone-iPad tethering doesn't seem to be an oversight. It seems like a carefully planned decision on Apple's part to keep AT&T happy. It is very possible for Apple to make tethering work via a software update perhaps along with a new connection cable, but I really don't see that happening since it will interfere with AT&T's iPad cellular connection plan pricing while maintaining the value of charging an extra $130 for a 3G-enabled iPad.
I understand that this is a business decision and that making as much money as possible warms shareholders' hearts, but to me this premeditated decision is dirty pool and another good reason to Jailbreak your iPhone.