Syrians are going no where... Syrians will stay in Syria... But they will get their own "Syria"... under another leadership that isn't ASSad...
You may don't like it... But the other 10Mil Syrians that are either Refugees or in rebel areas WANT something without ASSad...
And for that... they can't do it alone... you need a sponsor who can fight/sustain your fight... That's where TR comes in... and Therefore to have a future for them... you will need that "Desert" and it's ressources otherwise what you feared could happen, that is annexation or assimilation, since those refugees will stay under 100% TR goodwill/society
I don't see TR keeping them like that, so it's will be like Northern Syria..Annexation of that Buffer Zone+Idlib and Refugees becoming sort of Turkish and whatever comes with it.
So in the End... taking that Desert will answer to your worries. and it's a win-win for everyone... For you to keep Syrian identity/Land under Syrian leadership and for Turks to get ride of Refugees and answer to their worries.
Without it...it's lose -lose... Syrian becoming Turks and you losing the "identity/land card"...