I think the answer to that is that they sell every JK they can make, so there is little pressure to make changes. Cynical, moi? ;)
I suspect that the ZF 8-speed may be a somewhat different size than the current slushbox, making it a much larger job to use in the current platform. Maybe someone...
Not sure what you mean by "Auto 4WD". My 2002 Liberty has a transfer case with 2WD, 4WD Lo, 4WD Hi, and FullTime 4WD. In FullTime 4WD the transfer case is open. In either of the Part-Time 4WD settings, the transfer case is locked so that front and rear move at the same speed. At 173,000 miles...
I just hope they offer a transfer case that gives us:
2WD
4WD Hi
4WD Lo (with lockers available)
Full-Time 4WD (for use on any surface, including dry pavement)