I personally think Kennedy while a conservative is very sympathetic towards gay rights, having previously struck down a voter-approved amendment to the Colorado constitution and writing the majority opinion in a case challenging a ban on LGBT protections. He is known to have gay friends, and I think he probably personally supports same sex marriage. Question is, will he go from Reagan appointee to gay rights hero and use the Prop 8 case to declare a right to same-sex marriage nationally under the Equal Protection clause. This was hard to see him doing prior to John Roberts shockingly bold decision to side with the liberals and effectively single handedly save Obamacare... But I think now anything is possible and this may just have given him the courage to do it. The other perhaps more likely possibility is that he may vote to overturn the entirety of DOMA, meaning other states may have to start recognising (but not performing) them.
I can't wait. Triple whammy of liberal decisions after the immigration and healthcare ones. And who said it was a conservative court?