First of all, I think it is highly premature to be thinking about the Try Transit Festival, which now usually takes place in the Fall (for a while they had it in May but it's been back to Fall for several years). This date in the Fall can fluctuate anywhere between mid-September and mid-October, depending on other scheduled events in the area, the Jewish holidays, etc. So we are still 5 or 6 months away, and a little over 6 months since the last one.
Was it really all that great? I think many railfans agree that each year that festival has diminished somewhat, as there is less and less to see. Although I can claim I have not missed a Hoboken Festival (as they used to be called) since 1984, I don't think I will feel cheated if they choose not to hold one this year. The 2002 event had something missing, mainly because they decided to hold it in conjunction with a street fair going on several blocks away. Thus many of the usual vendors were out at the other part of the festival that had nothing to do with trains. They have missed holding the festival on two previous occasions, both due to station renovations.
The excuse in your response about our nation's security, while a serious issue, is a cop-out. As Alan said, so many commuters funnel through that station on a regular weekday, so is the terminal unsafe for them too? I bet if you made their response public, sending it on to the Newark Star-Ledger, it would result in a lot of angry letters from commuters who wonder why their safety is being compromised if NJ TRANSIT does not want to hold a single event one weekend day in the same terminal for fears of it being a security risk.
We've all been well aware of the possibilities of terrorism since September 11, 2001. It was just three days before that when many of us stood at the Try Transit Festival in 2001, looking across the river at the World Trade Center, never expecting that it would not be there by the middle of that week. But in 2002, about 57 weeks after the 2001 event and the tragedy of 9/11/01, they held another Try Transit Festival, and even expanded it throughout Hoboken up Washington Street. True at this time we are at war, but everyone knows we are continuing to live our lives and enjoy our freedoms as we were before it started. We're just watching out for unusual things a little more now.
I think the reason for the response you got is two-fold. It is too early to commit to having a festival in Hoboken. I think that saying our nation's security is being threatened, while remotely true, is not the reason they would come to such a decision. It may have more to do with money. Holding these festivals costs the agency money. It's hard to justify putting on such a show every year, when they have to deal with overcrowded trains, timekeeping problems, getting new rail lines and stations opened on time, and other headaches. It's hard to tell people to "Try Transit" when you are having trouble meeting opening dates and keeping the escalators running in a brand new Penn Station concourse.