Do you think he'll maintain his 571 ISO? He's more likely to keep that ugly 41% k rate. Doubtful that he continues to have a 28% barrel rate. He has 2 nice homers, I don't think he's going to keep hitting them.
If Chavis, Dalbec, Marwin and Santana all are hitting the way they are now, you'd improve the team by adding Casas. Sure, you can have a guy field a position, but if you can get better and are trying to make a run, why not go all in?
Dalbec has shown himself to be a bottom of the order hitter. Casas is a middle of the order bat. If they are in contention and Dalbec is still struggling, I'd be very tempted to bring up Casas.
I'm not sure the Olympics would be an increase in competition over AAA. It could be good for the guys to be around veteran players like Matt Kemp and others that fill out the roster though.
You do know that they can decide to promote him before the actual Olympics (Downs, too)? The preliminary round they are playing the next few weeks doesn't have to be the exact roster that goes to the Olympics.