http://www.cnn.com/2007/HEALTH/conditions/07/24/diet.sodas/index.html
While there is no absolute proof, this is one of many references to studies suggesting a link.
Um, your “study” does not mention the condition of the participants at the beginning of the “study.” Perhaps because the soft drink group was at higer risk to begin with? You don’t know, and that’s what I assume.
Take a thousand identical twins. Deny one twin softdrinks for life, and give the other three cans a day. Wait thirty years, and then get back to me.