I think you have to be a little worried he's not hitting. Like his offense is plus because he's walking like crazy, but when you make him actually swing the bat he's been...fine. And better pitchers will force him to do much more.
Kepley has an 86% contact rate, that's very good but it's not elite. He's hot a 45% groundball rate which is high but not quite problematic. He's got 14 XBHs including two dongs. Jeff McNeil, who the big club just saw, has an 86% contact rate, 45% groundball rate, and 11 XBHs including two dongs. Now good CF defense and a 50+ steal pace would changs the calculus even there, but it's worth noting that it's not all sunshine and rainbows even with his production so far.