I think you will see this for a while around large parades. I don't think there is a lot of danger from copycats, though there is always that, but more to make the people feel safe at similar gatherings.
After the Boston marathon bombing races looked very different for a few years as a result. Helicopters circling the course, DHS in full gear at the finish area, ID needed to get close to certain areas. I think you'll see a similar increase in both police presence and the use of blockades like Jersey Barriers for a little while.