Recent reports suggest that jailbreak for the 8.3 version of the iOS is about to come in the start of July. On this are working a group of Chinese hackers called Keen team or K33N. They are a very popular group of hackers and known for cracking Safari.
They will also try their luck on 8.4 too, which will come out in June 30th, hoping to bring jailbreak soon after they will reportedly launch it for the 8.3 version.
Regarding iOS 9 there is still plenty of time until the launch, so it is very obvious that their main target is working on 8.4 jailbreak. However, this doesn't mean they aren't getting prepared for that too, actually they are determined to crack the iOS 9 and bring jailbreak for the users as soon as comes out.