No indication yet how many jobs will be cut. There has been redundancies before at EMC/Dell out in Ballincollig but more jobs were subsequently added in the following years, more than replacing those lost.
General point is correct though - Ireland generally and Cork in particular heavily reliant on Foreign Direct Investment. We could take a hit of one or two leaving (chances are they'd be quickly replaced by others keen to utilise experienced workers) but we would be badly exposed if there was some type of global economic shock and there was multiple office/factory closures.
Of course if Apple were to close completely with loss of 6,000+ workers, that would have similar effect to loss of Fords and Dunlop's back in the day.