I wouldn't hold my breath. DeRozan isn't going to become a good 3P shooter.
The things most fans don't pay attention to could fill a book. Over the years, 95% of Danny Green's 3P's have been assisted. He's such a ball handler, he has virtually no responsibility for anything but shooting standstill 3P shots. This year something like 82% of White's 3P shots have been assisted, because he's responsible for keeping the ball moving so much more. I guarantee you, if White could stand out on the arc and take the same wide-open 3's that Danny has taken his whole career, White would be shooting something much closer to the 40% that Danny has made over his career.
With Murray, White, and DeRozan all three available to move the ball, I expect White to get a lot more opportunities to drop out to the arc and shoot open 3's. And I totally expect him to make a higher percentage as a result. And for those who haven't been looking, White rounds out his stat line with steals and blocks a LOT like Danny did. I expect the comparisons between those two to increase as he settles in here. Danny is a little taller, but White can score off the dribble better now than Danny ever has in his career. I think that more than makes up for the height difference.