“There are a number of gearing changes coming in 7.0, and we want to make sure players have ample time to gear up their characters, settle into Combat Styles, and get their groups ready for the next great threat to the Galaxy.”
Not only will this staggered launch of the R-4 Anomaly Operation let players acclimate to everything new in SWTOR, the devs reason this also puts into practice the overall gearing philosophy of players continually growing in power. The goal is to have this upcoming Operation arrive to PTS shortly after Legacy of the Sith goes live, so players should expect to wait a little bit in the meanwhile.
source: official site