For sale? Probably. For use? It's the same hashrate/power consumption per chip, the mini will continue to be profitable at the same ratio as the bigger guys, just less on a day to day level.
Also Z9 mini is realistically the only ASIC miner for mining at home without any special investment in electrical installation (even if you a have a few of them). The noise level is border line tolerable and it is using not much more power than GTX1080Ti (with the price of second batch with coupon, comparable as well)
Not at all, pretty much all Bitmain miners are usable at home without any electrical mods (provided your house doesn't have pre-60s wiring still); any 20amp circuit will easily suffice, and most of them run fine on a 15amp line. That said, ALL miners are more efficient on a 220v line, and the A3 and S9 both require their own dedicated lines (I assume the Z9 biggie does as well)...
Make sure to use a psu that will function on a 110v line at the wattage you need.