People tend to drive the speed they are comfortable at. If most people are already driving 70 - 75 MPH they are probably not going to increase by much, if at all.
I tend to target 72/73 MPH but would probably push it up to at least 75 with the new limit. I feel perfectly comfortable at that speed and even higher. Yes, you have a little less time to react in an emergency situation but at high speeds the time is already reduced. The impact of a collision could be a little worse but the impact of a 65MPH crash is already probably fatal.
Of course if you are uncomfortable at 70 MPH just stay in the right lane so I can pass you. Thanks.