Will it be available as a Gophone (prepaid service)?
"No, only available with a two-year contract." Pretty cut and dried there. We're also told that there will be no contract-free price on postpaid service; the one and only way to get in on this action will be to re-up your commitment to AT&T. Unofficially, we've been slipped information that AT&T's typical upgrade eligibility rules apply when signing the new contract, and there will be a separate (read: higher) pricing scheme for "non-qualified upgrades." These prices have not yet been set.
How does contract sign-up work when a customer is in an Apple store?
"You will need to speak with Apple for more details on their retail operations, but the activation process will take place in the store." That's the official line, but we're also hearing that customers in Apple stores may take their purchase home with them without being physically activated, in which case the activation process is completed later through iTunes. Either way, though, they're not letting you out the door without signing on the dotted line.
In AT&T stores, the process should be pretty similar, except that customers will be obligated to physically activate before they leave. The stores will be receiving "tether cords" to make that happen. Just a warning, AT&T: whatever software you're activating these puppies with is going to be reverse-engineered in no time, we'd wager.
What will the per-customer purchase limit be?
Official: "We haven't discussed this yet." Unofficial: at AT&T stores, we hear that the limit will remain three. Difference is they've now all got to be activated in-store, so that would be one heck of a commitment if you somehow felt compelled to buy more than that in one helping.
Will FAN (corporate) discounts apply?
Another "We haven't discussed this yet" for this one. Since the iPhone will continue to have its own set of plans, it's entirely possible AT&T could make them ineligible for discounting. The counterargument, though, is that the iPhone is now being offered like any other phone -- deeply subsidized by the carrier, that is -- and details of the device's service should fall in line with that as well. We'll see.
Apple iPhone 6s