Automatic motion blur in video editor?
Motion from Apple has a setting for Motion Blur on all projects. This section of the documentation explains how to set it (in the project settings). (It's under "Motion Blur and Reflection Settings".)

Once the project setting is set, you may also need to turn it on in the canvas to see it while editing. See here for information on turning it on in the Canvas. (It's under the section named "Render pop-up menu.")

Motion renders a lot of stuff in real time, though turning on Motion Blur will slow it down. You can always set the number of samples to something low-ish (like 4 or 8) while working and turn it up for renders.

I believe that if you're using a Motion template in FCP that it will render the Motion Blur if you set the canvas to "Better Quality" playback.