Probably a minor refresh for Haswell. I wouldn't expect too much.
Pure speculation, but maybe they had some integration difficulties and didn't want to commit to a specific timeline, or they couldn't release it /right now/ like the MBA so they wanted to hold off to fill out their fall event. There are a ton of other things that could have held it back; perhaps Intel isn't ramped up enough on volume production of the quad-core Haswells and they didn't want to just update the dual-cores first.
Exactly, that's all the MBA refresh was - much to my girlfriend's disappointment - no retina display (but if the Air got a retina display, there ends up being very little to differentiate between the Air and the new Pros).
Pure speculation, but maybe they had some integration difficulties and didn't want to commit to a specific timeline, or they couldn't release it /right now/ like the MBA so they wanted to hold off to fill out their fall event. There are a ton of other things that could have held it back; perhaps Intel isn't ramped up enough on volume production of the quad-core Haswells and they didn't want to just update the dual-cores first.