I just worry about the negative impact when the hard fork is taking place especially put into consideration the size of network we are having right now. I mean what if somebody plans a out scheme that manipulates the network during the switch over. But then if we think again, if we don't do it now, then the question is when are we going to do it. As the network grows there can never be the right time.... and we really need to plan, prepare and anticipate for the future.
I don't think a planned fork would make the network any more vulnerable to a potential attack then a time when the network is not about to get hard-forked. I would even argue that the network would be slightly more secure during this time as many people would be paying very close attention to the network and various aspects about the network