What can rugby tell us about the future of football?

A recurring question in discussions of the future of football in light of safety concerns is whether, and how, you can have a "safer" tackling sport. Thoughts generally turn towards rugby--dre did a workshop at FIU in February and this came up during that conversation. Having just watched the Tokyo Sevens rugby tournament, I wonder if the answer is in there somewhere. Without question it is a tough, brutal, physical sport and in all likelihood players are suffering some head trauma, as well as other physical injuries. But rugby seems to involve more tackling and less "big hits" or high-speed/high-impact collisions. Players (especially off the ball) do not get the same running start or head of steam, so they are not moving as fast when the hit one another.

So am I correct as to nature of the hitting and tackling in rugby compared with football? And if so, is there a way to change the rules of football and the way it is played to make the hitting more like rugby? And would it work to preserve football or would it so fundamentally alter the game?