Hopefully most of them will get killed if Turkey seals the...

Hopefully most of them will get killed if Turkey seals the boarder just like what the Jordanians did to the ISIS pocket down south. But they will be desperate to do some form of atrocity to gain international sympathy. Already these terrorists are rounding up local leaders and their families that they suspect have pro government or reconciliation sympathies. I suspect hostage situation like what occurred in the past.

Turkey will take those that want to join them as a way to escape in their Turkish area for greater leverage and some of the more mercenary elements will find employment with the Kurdish SDF as 'moderates' like with former ISIS members, I expect others will slip through as civilians to join ISIS or Al-Qaeda in Afghanistan, Libya, Central Asia or Egypt.

It will be hard to see what will transpire fully. We know the Chinese are on the ground to process their Muslim Uighurs (over 10k) and there is rumors the US met unofficially with the Syrian government to bargain including a request for terrorist intel, which likely means they believe many will slip trough to the West as part of the fighting. Their families will of course be welcomed in Germany if the past is any indication.