It's an interesting conundrum. I wonder if Apple are preventing Nvidia from releasing these drivers? I mean, we saw that youtube link where Nvidia were testing Pascal virtualised on older Mac Pros, so the drivers must already exist.
Perhaps releasing them or not is a purely political decision. Apple wouldn't want people to keep their machines indefinitely, and the Mac Pro line until the 2013 model us almost entirely user-servicable. It's reasonable to believe Apple would like to do all they can to make it hard to keep these machines up to date to force us to upgrade.
Perhaps Nvidia are in discussion with Apple over including them in future products, but a stipulation of any such agreement on Apple's part is that Nvidia not make Pascal available via driver support. That would make sense, but then Maxwell support is a bit of a mystery. Apple obviously wouldn't permit people to make 'Mac-compatible' products without their approval, not least of which because they include Apple's logos on the products et al. The 680 and the 7950 have full support, although that isn't entirely surprising, since the same family of cards are present in Mac lineups from the time (680m and 7xxx series 'Dx00' brand cards). Maxwell never got released on Macs though, so their inclusion on web drivers from Nvidia must mean that they aren't bound by Apple not to release something like that, though I doubt any Nvidia partner today would be permitted to sell Mac-compatible GPUs. AMD obviously have closer ties to Apple these days, surprising they haven't, but then perhaps that's part of their agreement. AMD get to ship cards in Macs, don't develop web drivers themselves for products not shipping within Macs.
Something I've wondered for a while too, the 7950 and 680 Mac Edition cards were rather unusual. Correct me if I'm wrong, but is this the first time Apple ever allowed this? Especially since they went Intel? I wonder if Apple were going to launch the 2012 Mac Pro 'update' with these GPUs, then got cold feet and cancelled it at the last minute, but the EFI/driver work had already been done? They did come out a while later, (2013 is when I bought mine), so perhaps partner companies were allowed to release them separately?
Seems a bit heartless, but ultimately, Apple have to make a profit. Even if these machines did cost a lot when we bought them, all they're really interested in is selling us new ones. I think a lot of people evangelise Apple as some paragon of virtue, but in many respects they're just like any other big technology company.
