No ETA but note that the driver itself is ready (it's based on the AROS one), but the configuration tool was not done yet.
If lucky the MorphOS team decides to provide the pure driver (i.e. w/o config tool) as is and w/o warranty for the brave (or stupid) to try out (until it will be integrated inside the OS with 3.1).
AFAIK That's the driver for an pcmcia based Atheros chipset, not the onboard 'AirPort Extreme' wifi.