He's starting this season in Double A so he's not that far away.
He'll put himself in position to come up in 2018 if he has a good season.
The Yankees are notoriously slow with prospects.
He would have to crush it at AA this year and even then he won't go straight to MLB (which sometimes does happen).
Most likely scenario is this:
Barring an injury at the SS position, and assuming that Gleyber rocks it at AA, he gets promoted to AAA to finish the 2017 season.
Gets an invite to Spring Training 2018.
Gets sent back down to start the 2018 season in the minors (assuming this affects his Super Two status).
If he crushes it in the Minors and the ML shortstop position looks terrible, you'd see Torres in the Bronx in the middle of May or early June of 2018.
Torres isn't the prospect that Corey Seager was, and it took Seager a while to get called up in LA.