Simply can not tell whether Stabiliser came off in flight or at impact from the pictures, however I suspect there is a good chance they may be able pin down a good estimate when it is carefully examined. The way everybody is amking announcements (though n ot always accurate) there is a good chance we'll hear what the likelyhood is when they get it back to land and examine it.
As a PPL and not anything to do with engineering either I was slightly astonished on learning of the standard set for stabiliser attachment after the AA chrash. I realise this is not just an Airbus thing too, and perhaps the engineering required to fix structure for high speeds would be just so out of order that travel limiting is the only reasonable option.
However looking at the type of attachment, rather like that fixing a keel on a high performance sailboat, one can not but be concerned at the moments and leverage involved and wonder why, if it is attached behind the after pressure bulkhead, they did not go for a lower leverage design with loads spread between the upper and lower fuselage construction.