It appears that someone at AT&T has leaked an internal Q&A document. The document mostly confirms information that we already knew, but does answer a few questions.

Here are a couple of the questions that are answered:

Q. If I am an existing customer, can I upgrade and will you give me an upgrade credit/subsidy for this device?
A. An existing customer can purchase the iPhone for the same price as a new customer. However, no subsidies are being offered on the phone at this time.

Q. If a customer is at the end of their contract prior to launch and want to wait to upgrade, what should I do?
A. If a customer is at the end of their contract or is no longer on a contract and wants to wait to upgrade to the iPhone, we will allow this. QA scores will not be reduced for allowing the customer to wait to extend their contract in this scenario.

The document also confirmed that the iPhone is on track for a June release.

AT&T iPhone Q&A for Employees [via macrumors]