I don't know if anyone has noticed, there has been a big shake up at Apple developer forums. They have basically removed developer support. Apple engineers used to respond to forum posts. So for instance, if you came across a nasty OpenGL problem, you could get help from the engineer that maintains the driver. Now, that is gone and you are basically on your own.

Cynical explanation: Apple is under-staffed (as evidence, consider the numerous times they've had to delay one product because the engineering staff were tasked with another, most recently the ?TV), and thus wishes to minimize non-development tasks that engineers have to engage in. In their stead, you're expected to "talk among yourselves."

On the other hand, Apple is consolidating their efforts around technologies they own, prioritizing Metal over OpenGL.

Ultimately, it's hard to draw any meaningful conclusions from it all.

I haven't noticed it at all. I have always thought the forums were user-to-user. The iOS Developer Program offers paid technical support if you really need it.

When/Where have they said that no apple engineers will post on the forums anymore?

It still says "Post questions and share thoughts with fellow developers and Apple engineers" on the link to it at developer.apple.com, and I can still see people with the "Apple staff" icon post in the threads...

Might be interesting if you could put together a crawler and nab out data of posts over time.

It is entirely possible that apple is still posting just as often as they've always been, but the overall volume of user posts has been increasing over time and drowning out the Apple Staff posts to make them less visible and appear to be effectively posting 'less' because a lower percentage of topics get commented on directly by them. (They could actually even be posting more in that case, but still be hard to see as such.) They could also be spending more time posting in other areas that you have less interaction with, or they could just simply be posting less often overall.

Data, and the perception of it, can be an interesting thing.

A good example of that is violence statistics. If you ask random people on the street then you can easily come away with a large portion of people saying that the world is more violent and chaotic than it was 100 years ago, while actual research data shows that the likelihood of death by violence has effectively been at an all time low world wide for something like the last 30 or 50 years.

When/Where have they said that no apple engineers will post on the forums anymore?

It still says "Post questions and share thoughts with fellow developers and Apple engineers" on the link to it at developer.apple.com, and I can still see people with the "Apple staff" icon post in the threads...

I searched through just now. Indeed, there is one or two replys from Apple employees in some of the forums, but not in the important ones (i.e. I mean no replys in any graphics forums)

Upload a security hole on github with instructions on how to use it in the Apple Dev forums, and they are sure to respond (no, really, don't do that).

Could it just be a combination of WWDC and the impending iOS9 that has made Apple engineers very busy recently?