IDK that Acuna keeps a .340 BABIP, but he probably also won't strike out 28.7% of the time going forward which should eventually get the BABIP lower anyway. I see more around the low to mid twenties. I think next year he's probably about around 8-10% BB and 22-24% K.
In 2017 he was a 21%+ LD hitter at all 3 levels and interestingly, at AA-AAA he was at 36.2% FB and 30.2% FB and yet he knocked 18 HR just at those levels. This year he's pretty steadily stayed around 40%. Considering that the power is very much real though, with him its not that big of a deal.
Acuna is the type of player with high exit velocity you want hitting FBs. A low BABIP from him is fine when it comes with a huge ISO like he is likely to produce.
No matter what, it's pretty clear he is going to be an impact bat.