Looking forward to the fix, really makes some pain.

As a workaround, you can dispose www in another thread.

private void DisposeWWWInBackground (WWW www)
{
new Thread( () => {
Debug.Log("WWW dispose started in background thread.");
www.Dispose();
Debug.Log("WWW dispose finished.");
}).Start();
}

Any workaround for this now?

We are also seeing this same bug. We start a co-routine with this code:

WWW www = new WWW(url, System.Text.Encoding.UTF8.GetBytes(postJSONText), postHeader);
bool hasTimeLeft = true;
while (!www.isDone && hasTimeLeft)
{
yield return null;
hasTimeLeft = Time.realtimeSinceStartup <= startTime + _waitForDownloadSeconds;
}
if (hasTimeLeft) //We didn't time out!
{
//Do some stuff.
}
www.Dispose();

If the internet is slow and _waitForDownloadSeconds occurs before WWW.isDone the game freezes.