Historically Blizzard has always announced the end of a PvP season 2 weeks prior to a patch dropping and gave the precise date 1 week prior. This time the end of S4 was announced two weeks ago but a precise has not been given today. The end of S1 was also announced 3 weeks before it actually ended but a date was given at the end of the 2nd week. Right now it's already too late to give a date this week so the earliest we could get 7.3 is the 5th of September. There's no release candidate on the PTR either.