I really don't understand what all the fuss is about.
It isn't like we haven't had adults roaming the halls before. I've seen visitors from the Ministry here every year since we got to Hogwarts. Even my sister told me they went through this when she was at Hogwarts, and that's been years ago. There's always some scare and some rumor that gets started and spread like wildfire until all of the students are convinced that something is about to happen.
It seems like every journal I've looked at today has some comment about how things are 'weird' or 'wrong' or 'tense.' I even read one about a strange dream that I'm sure everyone is immediately going to assume has some grand significance.
Trust me, if something big was going to happen, I guarantee I wouldn't have had to try to struggle my way through Herbology today.
Do you really think the professors would have us running about the hallways and actually walking back and forth to the greenhouses if they expected someone to jump out of the Forbidden Forest at any minute to grab us?