Its allies will stick up for turkey and the EU especially does try to help Turkey a lot. Also in terms of what Russia is going to do it is all just posturing, Russia's economy is is already weakened and these sanctions against Turkey will hardly make a difference.
There is no guarantee that the European Union will help Turkey beyond a certain point. The EU has enough problems of its own, with some of its member nations (Greece, Spain, Portugal.etc) close to bankruptcy. Also, they are struggling to deal with the huge migration inflow, which is likely to cost them at least EUR 100 billion per year from 2017 onward.
