Even once the next via bulletin is released, there will still be no way to estimate how long this will take -the dates don't progress on an "x" numb er of days per "y" number of days basis; the formula is not known to the public but apparently includes such things as how many of these cases have been approved overall, how many they have received for final-stage processing, etc.
The dates can sometimes go backwards as well as forwards, and large leaps in either direction are common - as are long periods of no movement.
Could not have answered it better than Attorney Reich! You just have to keep looking at it every month. Sometimes it goes back and even way back and sometimes it moves forward by more than a few months.