-- Increased IPv6 support -- likely.

-- Updated window graphical user interface (GUI) to solid rather than brushed metal (a la iTunes) -- possible. (Apple does tend to update the operating system to resemble the interface used in the iLife suite and has a tendency to update the GUI as a whole every couple of years.)

-- Increased home directory options -- possible. (One possibility: an iPod-based home directory, though I'm not sure of the practicality of this.)

-- More full-screen application use -- possible. (iPhoto has definitely made excellent use of full-screen editing, and I can see that option carrying throughout other bundled applications.)

-- Increased home entertainment integration -- very likely. (Apple has done a great deal to make Macs into the "digital hub" that Steve Jobs described a few years ago. Improvements to Front Row have really made the Mac a media center, and it seems almost certain Apple will continue pushing the potential for home integration.)