It’s been this way since last week. There’s not even a shipping delay — it’s just “currently unavailable”. They won’t even let you place an order.
- The iPhone is being updated. Extremely likely, but the timing is strange — everyone, including AT&T, seems to be assuming that the update will come at Apple’s WWDC conference on June 9. It probably isn’t a good idea to prevent people from buying your flagship product for an entire month, but it’s also unlikely that Apple would update it without a significant press event — and the only event on the horizon so far is WWDC.
- It’s simply out of stock. This happened before, and everyone speculated about an update, but Apple quickly quelled any speculation with a public statement that they were simply out of stock and were restocking shortly. This is the more sensible answer, but it’s been quite a few days this time and Apple hasn’t said a word.
I’m voting for option 2, simply because option 1 has too many strange side-effects — most notably, I don’t think they’d launch it without a big event, and they wouldn’t schedule a separate big event so close to WWDC.