It may decrease but I'm not sure if it would be a significant decrease. He shot 47% from the field in a Mark Jackson offense while setting the 3's made record.
True, but spacing is less about offensive system and more about the players around him. You could take the same system, switch Klay Thompson with Demar Derozan run the same plays, but teams would help off of Derozan to stop Curry. Just like you could run the same system, switch Draymond Green with Blake Griffin and teams would help off of Griffin to stop Curry. It's irrelevant if a coach puts a player at the three point line, any coach can do that. The question is if the guy at the three point line is a threat. For example, I'm a big Wiz fan. As soon as Wall gives up the ball on offense, he runs through the lane and exits to the three point line opposite of the side he passes the ball. After Wall parks on the three point line, is man immediately sags off and helps because he knows John Wall isn't a legitimate threat to beat him from deep. Now if that was Damian Lillard or Steph Curry doing the same exact thing, in the same exact system with the same exact coach the defender would be on them like white on rice.
On a deeper sense what I'm trying to say is that an individual players efficiency is dependent on the players around him and their skill sets. The more three point shooters a team has, the less individual defenders can help when Steph has the ball. This doesn't mean that Steph isn't a great player, but it does explain why he is having the most efficient season ever.
Steph was always a beast, but if this Steph Curry was playing the players on that team...Monta Ellis, Andris Biedrins, Ronny Turiaf his efficiency would go down regardless of if Steve Kerr was coach. Klay Thompson and Draymond Green are the perfect compliments to Steph's game. And here's another point, if KD goes to the Warriors next year, his efficiency will go up.