Let's focus back on the question, therefore.
1. Turkey at the moment is defacto allied with ISxx, as they are knocking the stuffing out of the Kurds. The Turkish Government has nothing to fear from reproaches that they did nothing, as all they have to say is "we took in millions of you as refugees", and yet at the same time they are able to divide and conquer a possible problem.
2. That may seem shortsighted from a Western point of view. But at the same time, it is our self-interest which paints it that way, Turkey asked long enough to join the EU and was consistently told that they need to resolve their human rights policies such as this, and so no longer feels it owes Europe anything.
3. IS, having secured its rear, may either continue to milk Iraq, or more likely turn right into Jordan and Israel. King Abdulla's alignment with the UK from his Sandhurst days must make him an appealing target.
4. If it does continue through Iraq, it's next step will be into the Gulf, to increase its grip on fuel supplies. However, it is still small, and relies on mobility: towns tie their forces down, and make them vulnerable to attack. At the moment, the air forces are based too far away to respond tactically. However, if IS were to attack Turkey seriously (by which I mean the heartland, the Turks will be only too happy to see the refugee camps cleaned out - yes, that's genocide, but they won't be the ones perpetrating it), then IS might find they get bogged in.
5. In dealing with the Gulf, they deal with their brethren the Gulf Salafi, who are not the most genteel rulers. In this, they have to hold their heads high with a reputation for brutality, as they are dealing with the likes of Nasr al Khalifa, who's just made the headlines for butchery. I had the somewhat interesting pleasure of the Prince's hospitality ealier this year, as he needed my advice on something, and in prson he is both highly cultured when it pleases him and utterly lethal, very much the Medici Prince. Thankfully I did not have the duty of telling him where he got off, as he threw his toys out of the pram: he is now wondering exactly who he was talking to as he never expected to have an International Arrest Warrant against him. But never for a moment in dealing with these think that they have any interest other than their own as leaders of their tribe. Their money maskes them capricious at best, and homicidal at worst: and it is very likely that the idea of a viable Califate will pleaase them. However, it will also cause serious behind-the-scenes infighting as they will all see themselves as Calif and will NOT appreciate the power behind the throne being quite so apostate as IS.

One aspect the West needs to think about, and quickly, is that if it does not do something quickly to build the Kurds, then Turkey will have to clean the house, leaving them with a hegemonic claim over Syria and Iraq. Are we really happy with that thought?