The death of an Isis ringleader will have a negative effect on morale. However, it may also serve as a rallying point if the dead leader is seen as a martyr. Hopefully, numerous ringleaders will be targeted and taken out over the coming weeks, weakening the core leadership and undermining future terrorist plans.
ISIS recruits young fighters on the basis of reward for service. They promise virgins in their afterlife, comradery to many men who feel excluded from society. The argument that this killing will demoralize ISIS is contrary to the message of ISIS, rather a reinforcement to the compelling words of the recruiters. They can allude to these killings as examples of brave acts and will until death of their fighters, their commitment to the State.
ISIS' beliefs are so deeply rooted in their fighters that the death of a leader will not stop them. At the rate they are recruiting now, they could just replace him. I won't say simply because it's not that simple, but still. They believe in fighting to the death to achieve their goals, even bringing down innocent lives with them.
No, death of the ringleader won't change a thing, because this terrorist cell is destroyed anyway, That is the whole point of the "cellular" structure. Each cell is independent and if one gets destroyed, some other will be activated. The only way to make an impact is to target the top leaders of the ISIS.
Just like the death of the previous leader, which gave birth to the current leader of ISIS, to kill the current leader of ISIS would only give rise to another leader. This idea of death for one's country is ingrained in these people from birth, therefore their fight would never end until their life is ended.
No, I don't think it will have much impact on the war against ISIS. The terrorist group is recruiting at an insane pace lately it seems, using social media outlets such as Facebook and Twitter. He will be replaced and the terror will continue, unfortunately, until something is done on a much broader scale.