We are talking GEGA
not MEGA bits per second.
So if your coax is getting you 3 MBPS, Internet 2 would give 10,000 Megabits per second
Look here for more tests that have been done:
http://lsr.internet2.edu/
Once this becomes commercial, I guess the sky is the limit on how many 1000s
HDTV channels you will be able to receive using your Internet connection. This could be 10 years down the road, I don't know.