Apple has already started removing optical drive in its computer with the MacBook Air, and the recent models of Mac mini are also offering a dual HD unit instead of an optical drive bay. It is highly anticipated that the next generation of MacBook Pro will lack optical drives. IT could maybe still be integrated in iMac but will have to migrate to BD drive then.
Microsoft has decided to follow another strategy to send sign that such component are not needed anymore as technologies have evolved and we are moving towards Cloud storage and network/streaming offers. Windows 8 will not support video DVD playback, as it will lack the software components required for MPEG2 decoding and CSS protection.
As for the Mac, it will be possible to plug an external optical drive and use a third)party software, but this is a step towards the end of the optical drive in customer market. among the reasons for such move, and beyond licensing, it is a decision to push customers towards cloud and VOD offers, something that both Apple and Microsoft directly offer, and by removing support to optical drive, it will strongly attract customers to dematerialized offers.