I doubt Shinn can kill Kira. Kira has Ahtrun as Friend, Cagalli as Sister and Lacus as Loved one. Taking out kira would collapse who series put relations in chaos. Besdies it wasn't Kira who killed Stellar. If Shinn will hold someone responsible it will him and Neo. He trusted Neo and Neo gave her word to keep Stellar safe, he broke it. Shinn also attacked Stellar. So no way, I don't really see change that Shinn would kill Kira. He might bear grudge against Kira or I think this is perfect way to mature up Shinn and make him real hero instead that whining little, arrogant brat that he has been.

Even Kira fought in Orb battle I don't really recall that Shinn saw Freedom there. Only Murasame's. Shinn if I'm right at that time Freedom and Justice were closer Murasame research facility to cover mass launcher... If anyone Shinn blaims his family's death, it will not be Kira but Cagalli, because she is Athha. Daughter of Orb's leader, who'se principles made EA to attack Orb and forced Orb forces defend Orb...