Let's say he has this line in 600 PAs:
600 PA 550 AB 165 H 50 BB 40 2B 5 3B 15 HR
That is a .300/.358/.455 slashline good for an OPS of .813.
Don't think he can hit that many HRs? Then let's say he does this in 600 PAs:
600 PA 550 AB 165 H 50 BB 45 2B 10 3B 5 HR
That is a .300/.358/.445 slashline good for an OPS of .803.
So if he's a .300 hitter, a .800 OPS won't be terribly difficult for him to achieve. That said, if the 70 hit tool develops and is paired with 70 speed, he could hit a lot better than .300, especially with how little he strikes out and how much good speed positively affects BABIP.