I've been encountered with the WiFi device missing completely with recent snapshots, currently dd0ad9b661b604163d1736fcfe18714ff47c3728.
The symptom is the WiFi completely gone. Checking cat /proc/interrupts output and found there's no interrupts for the WiFi chipset as usual.
My device is D-Link DIR-860L B1.
I thought it will recover in a couple days but the issue still there. Just tried a sysupgrade with -n options and confirmed the WiFi chipset not presented.