I definitely seen them used in that manner... but at only 8 pins (two of which are probably power), its hard for me to imagine good future-proofing in only 6-pins.
I guess 28-pin CPLDs are already made though (Atmel ATF750C). But I really don't see how a 6-pin FPGA can be used for routing / future proofing.
all IC pins are available, 5 normal I/Os arranged as DIP8, the "LED IO" also usable as input or opendrain output are in the innner rows where you can solder 6 pins down, or socket "up", so all 10 I/O are available.
I guess 28-pin CPLDs are already made though (Atmel ATF750C). But I really don't see how a 6-pin FPGA can be used for routing / future proofing.