It looks like only 5 AAA teams are owned by the parent club, including now Syracuse. Maybe it becomes the next trend, but it's not remotely a league wide practice.
In the international league, The mets, braves, red sox, Yankees, and Indians own their aaa affiliate. A third of the league seems like a decent number. I'd like to see them make a run at buying Norfolk, or just found a team locally and refuse to sign a player development contract with anyone not willing to move