While I haven't dug deep on this trial, other cancer trails DSMB updates were not designed to occur on a specific date. They were designed to occur after a specific event. in all the cancers trials I have followed the specific event was a certain number of deaths. as such, there could not be a specific date, just an estimate.
An it makes sense for this trial also because part of the look by the DSMB is to make sure that people in the trial are not adversely affected in a negative way. (dying)
Again, I am not sure about this one but I would not be surprised if it goes long. actually, if this is as I have seen in the past, a longer wait could be beneficial as it could hint the drug is working well.