threat for XP obviously meaning that if more apps will require graphics hardware acceleration, those same apps won't run on XP, nothing else.
More apps are always going to take advantage of what hardware and OSes are recently released, life hasn't changed. The old adage of 80% of the users only use 20% of the functionality (bells and whistles, etc.), I feel is particularly true in many cases. The manufactures have to introduce new features to try and entice people to purchase and current users to update.
The actual worth of many of these features are unlikely to be used by the average user.
Just because they introduce hardware acceleration doesn't mean it won't work at all just that you won't benefit from any hardware acceleration if a) your hardware or b) your OS doesn't support it.
There is still in the region of 60% market share for XP or there was not to long ago and ignoring that volume would be crazy.