Okay, some things are changing at PrimeSense.
According to this post on I Programmer, the OpenNI website is set to close on April 23rd, just over seven weeks from now, plenty of time for those involved to download the latest version of the SDK, which they'll want to do as I see that the version sitting on the parallel GitHub site is not the latest beta, more likely the latest stable release.
If you have another look at the OpenNI website, you'll notice that there are Windows and Linux versions of the SDK. Considering that Apple has no clear interest in supporting development of the software on these platforms, the wonder is that those versions are still there, months after their acquisition of PrimeSense, not that they have set a date for pulling the plug on the OpenNI website.
Anyone who cares to will be able to pursue development of the (necessarily forked) version of the SDK that will continue to be available through GitHub, on whatever platform they choose. Being middleware, even if Apple were to cut off the supply of PrimeSense chips, OpenNI will continue to have value as it should be possible to make it work with other sensing hardware.
For their part, Apple is sure to make a derivative version of the SDK available through their iOS and/or OSX frameworks (eventually both, undoubtedly), as part of some future version of Xcode.
In my view, Apple's enlightened self-interest would dictate that they should continue to make PrimeSense chips available, not the latest designs of course, but about two years after they first find their way into Apple products, by which time they will have been reverse-engineered by competitors multiple times anyway. If Apple can maintain a technological lead, then their two year old designs should still be competitive with current designs from competitors, especially if priced at a low multiple of the cost of production. Likewise, they could safely contribute two year old frameworks to the GitHub-hosted OpenNI project, in the certainty that in doing so they would not be giving away any secrets.
By the same reasoning it could be to Apple's benefit to make their older SoC designs available as parts – say beginning with the A4, after it has been retired from Apple's product line – and to cooperate with smaller companies seeking to incorporate those chips into microcontrollers or similar products. This would be a way of recovering residual value from the expense of developing those designs in the first place.