"European customers cut their demand by 15 billion cubic meters last year, or 8.5%, while sales to the former USSR (mostly Ukraine) fell by 19%, or over 10 bcm. It’s no exaggeration to say that they will prefer any alternative source of gas (except maybe the shale under their own feet) to Gazprom’s as long as economics will allow them to."

That is much too simple. Primary energy esp. NG demand is determined by weather in central Europe, around 45% of the German imports are used for room heating, 45% for industrial process heat and <10% for generation of electricity.

2014 was a very warm year, therefore, demand for heating fuels was low, first six months of 2015 were much colder and as a result NG consumption was higher (IIRC ~3%) than first six monts of last year.

The second aspect is that there is a huge excess capacity of coal fired power plants in Europe (as a result of the German energiewende and economic crisis), which provide cheap alternatives in the fields of electricty generation and CHP, NG lost around 30% of its share in the German electricity market after 2010. This happened without any changes of the German energy policy, the European picture is very similar.

At least in Germany we do not see a shift from Russian sources to others, instead a general reduction of demand and it is a save bet that this development will continue as new buildings have a much lower energy demand than older ones. The long term perspective is IMHO a 1% annual demand reduction.

On the plus side for Gazprom is the fact that domestic European production of NG is decreasing and LNG is more expensive than Russian NG delivered by pipelines.