Probably never, the next version of PTS will most likely be 1.6.0. This is because PTS maintenance never happens on any day other than Monday, and next week the ZOS maintenance team will definitely not be around due to the holidays. Work usually resumes on 5th Jan and that's when we might see Update 6.
It's likely that we'll wait to update the build on PTS until we're ready to push Update 6. We'll be sure to let you know if that changes as well as when Update 6 is heading to PTS.