Correct me if I am wrong, but wasn't 24th of June the start date of WP 8.1 lifecycle, NOT the mass release of the update? I haven't seen anywhere a serious news source to claim that MS would release it today..
The way I see things with the release is that the update itself is ready, but they are waiting for Cortana team to launch all the features, planned for the release, since Cortana is in the core of the whole WP 8.1 and WP 9 experience for the future. Imagine they launch 8.1 today, without Cortana even showing your local news feed, temperature in Fahrenheit only, 10 jokes in total, and limited chit-chat.. that would be a disaster for a start.. launching an incomplete piece of software that is not 100% sure that will do what it is supposed to, would ruin everything, even though we all know what the plan is and how great Cortana will be..
Another thing to consider is that the official WP 8.1 SHOULD update Skype, as it is also a core product of the OS. There were news that Skype for 8.1 would be very different from what we have now.. I am not sure if Skype would be ready..
I am afraid if they launch the 8.1 before they are ready with Cortana and other details, they would ruin the whole OS. We, here that tested the new OS really don't care so much of the bugs or incompleteness of some software or missing one, but try to give feedback and work to make the OS better. Out there are many people that will not give Windows a second or third chance if they mess things this time..