Highly unlikely that it points towards premeditation, and zero - zero - chance Zimmerman is convicted of murder rather than manslaughter on that basis alone (if there is indeed evidence that Martin was on the ground and shot by a standing Zimmerman while begging for his life, that would be a different story.
Most people who would have a legit claim of self defense are rarely following someone they have already acknowledged as dangerous and potentially a criminal. The notion of self defense is based to some extent on initiation of contact. In this case everything points toward Zimmerman initiating as part of his mind set as neighborhood watch, carrying a gun and pursuing after calling it into police. Might that point not just away from self defense but toward pre-meditation?