Open borders shut?

Are we seeing the end of Schengen?  We (perhaps wisely in retrospect) were never in it, but the idea was that EU citizens could move freely between EU countries without border checks or the need to show passports.  But it was never intended to give free right of passage to those non-EU citizens who had somehow managed to get into the EU, and yet that's what's happened.  Of course, if you don't have to produce a passport or some other form of ID how do you know who's an EU citizen and who isn't?  And therein lies the inherent weakness in the system which is now being highlighted by the current immigrant crisis. Walls and barbed-wire fences going up all over the place - but will they ever come back down?