The Heroes of the Storm forums announce that the play test realm is now closed as they are right now in the midst of launching the new Eternal Conflict update for the MOBA. Word is:

Once the PTR closes, you will no longer be able to log in to the test realm until our next PTR phase. Thank you all very much for taking some time to give the PTR a spin during the past week. Your feedback and bug reporting have been very helpful.