There is no large substantive change in hackintosh stance here.
The relatively small lunatic fringe that wants to hack around "in the basement"/non-commercially with tweaked Macs and PC and hodgepodges of combining the two are largely free to continue what they have been doing. Apple doesn't particularly approve, but as long as not being a significant nuance they will take some losses as price of being in the game.
Besides to some extent it is free R&D. If they discover some combo that makes a big diff or find bugs or exploit weaknesses this is a why to find and track those to be fixed over time. It is also an outlet relieve value effect.
As much as the flashed-video cards were a funding source for hackintosh activity ..... this move actually reduces that. (flow of money into funded into taking more money out of Apple's market is not going to put you on Apple's christmas card list. )
Apple not using a mainstream card as the reference design and not adopting bleeding edge GPU cards will keep the hackintosh momentum to a minimum. There won't be drivers for the bleeding edge cards to even hack.
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This is a very good point..i also think that the main fear is on how Apple managed the Gpu in the past..but given how they built the Imac 27 with GTX680MX i really hope to see this machine with changeable (Gpu) parts within...well i'll be really happy to find that"
It is obviously replaceable/serviceable. Even Apple's website animaton shows it coming out. An open market for replacements is a different dimension.
Given the circular aspect of the cylinder is driven by a fan.... Yes they have.

Largely relying on low density air convection was never going to work well.
Jumping back into the pick shape before function zone. Not going to work.