Whilst I can't say for sure about any particular NIC, I should point out that my archaic telmexatapi PCMCIA ATAPI CD-Rom controller worked flawlessly with OS4 since last year. Furthermore, despite using the existing 680x0 telmexatapi.device, there is no discernable slow down compared to using it on the 040 with 3.x. Doubtless the sheer latency of the PCMCIA slot itself is the limit.
This indicates that the 680x0 emulation is sufficiently capable of handling various odd devices that perhaps wouldn't otherwise get an OS4 native driver. I expect, given the popularity of PCMCIA NIC's, there would be some OS4 native support sooner or later.
I haven't tried my spare NIC yet since my whole 1200 is misbehaving at present :-(