BGR (they have a good track record of these things), it's been confirmed that the new iOS 4.3 on all iPhones will have the Hotspot feature! It was told in the Verizon press conference yesterday that their iPhone 4 on the Verizon network will have the personal hotspot feature, but now it's been confirmed that all iPhones on iOS 4.3 will have that as well.According to
I'm pretty sure that the carrier will need to be able to support this feature, and amongst other things late with AT&T, it's possible that we may not be able to see this feature right away (AT&T is always slow with the coolest features). Anyways, you'll be able to connect up to 5 devices over Wi-Fi to your iPhone's data connection.
Here's some screenshots courtesy of BGR.