Whatever effects there may be in humans, the risk to an individual user is likely to be very small indeed. Expect large numbers of people to come forward with claims that a wide variety of conditions have been triggered or made worse by use of mobiles. These claims will be extremely difficult to prove. Even if a link is shown, proving that a particular case was directly related is almost impossible. This has been the case, for example, over Gulf War syndrome, or reactions to MMR vaccine, or the debates over passive smoking, or clustering of leukaemia cases near power stations.
Some manufacturers already sell radiation shields for mobiles, reducing radiation to the head.
Expect others to follow.