According to 9to5Mac, the latest beta of iOS 4.2 for the iPad (released to developers two days ago) carries a section within the APN network settings that clearly shows several "Internet Tethering" options. The tethering appears to be traditional Internet tethering, rather than using an iPhone's connection to power the network on an iPad.
The section asks for a username and password which is exactly what the iPhone sported before it gained official tethering. It certainly seems possible than Internet tethering will be coming to the iPad sooner than you expect, and could be landing as soon as iOS 4.2 is released in November.
It is important to note that the screenshot above is an iPad running on a 3G network in Europe, not on AT&T's network in the U.S. The setting could not be found on an AT&T iPad.
