Apple Watches do get discounted pretty quickly, wouldn't surprise me if you saw $30-50 off and/or some gift card promo during Black Friday... though, maybe supply chain issues might keep production closer in line with demand this time around, who knows. if stores have any remaining stock by then, the Series 7 will probably see larger discounts than it currently is.

if you get a cellular model and service, yeah, you can make phone calls and send messages without having your phone on you, stream music from Spotify/Apple Music, whatever. you can connect to WiFi networks in a gym or wherever as well if you just want to leave your phone in the car/at home and don't want cellular service and you can download music to the watch (though, apple does have rather asinine storage limitations)

Given that none of us have access to time machines, your guess is as good as ours.

Don’t buy the Series 3