I don't think they would have taken on this case if Kennedy wasn't ready to join the right side of history.
The only real question is if Roberts joins him.
If Kennedy continues to suport court mandated ssm, roberts will join for legacy reasons. If Kennedy joins the against sidea roberts will stay there.
With the split circuits, it was inevitable they'd take this case, so the decision to do so doesn't let us infer anything about the eventual result. I think Roberts will try to come up with an argument that lets this be a 6-3 decision, but if he can't, I don't see him being all that upset about letting it be a 5-4 decision.
Of the two issues SCOTUS is taking up with this case, the one I'm interested in not whether they'll decide to require states to recognize SSM, since unless there is an unexpected departure from the court they will, and even then at worst it'll cause them to hold off until a replacement is named to the court. No it's the one on whether states can be forced to recognize the SSMs of other states when they don't recognize them themselves. Possibly the court may decide the issue is moot if as expected they rule in favor of SSM. I hope so, because otherwise they may be dealing with a lot of topics that had been settled law beyond the narrow issue of SSM. Current doctrine is that states only have to recognize the actions of other states if the same action could be taken in that state itself and that minutae of how the two states might have differences in taking that exact same action shouldn't cause a state to not accept what another state has done. I hope they continue that. Imagine if you will if every state had to accept as valid the concealed carry permits issued by another state, even if they don't issue them themselves.