There already is a motion "blur"! Check out the attached image I took in 2011 with an EOS 350D + Canon 70-200 f/4 IS (what a *great* lens) and compare the shadow to the real scene (which are separated by about 2 m = 20 nsec).
I think I know what the mechanism behind this is, but I'm not 100% sure
I had not noticed for 3 years until coincidentally the kids where looking thru Picassa today and my wife noticed this very interesting difference. I've been to the Aussie Open twice since and have never managed to replicate the squashed tennis ball, beginner's luck?...maybe next year.
EB