Another factor is that EU demand for Russian gas is likely to increase... not decrease, yet some claim they already have plenty of capacity already...
The actual problem is that the Ukraine is an unreliable supplier and lets be honest if Russia cut off supply through the Ukraine right now the EU is likely to say they will cut off supplies via Poland or Belarus in protest... which means direct supply to Germany and Turkey make a lot of sense being a country that can say no to the EU and NATO and a country that can also say no to NATO and is not even in the EU.
The point is that gas piped to Turkey will give a lot of economic and political power to Turkey... but that likely wont be for 2-3 years yet.
I see S-400 systems have been delivered to Russian forces early, so an early delivery of Turkish systems would be very useful too...
Worst scenario is for some reason the US wins and the Europeans cut all gas pipelines to Russia and have to pay much much more for LNG from the US (it would hardly make sense to stop piped gas from Russia and replace it in defiance with more expensive LNG from Russia even if it is cheaper than from the US).
So the costs of production and heating go up in the EU... I am sure Japan would consider a gas pipeline... cheaper energy would not hurt their economy.
Probably the easiest solution from the Russian point of view in this worst case scenario would be to sell it all to Turkey and let Turkey sell to the EU... now if Erdogan was smart he would cooperate with Syria and encourage gas pipelines through Syria to Turkey from Iran and potentially other states in the ME and then they could pipe gas to the EU from Russia and Iran and be the gas kings of the EU... Don't get involved in internal problems... once the gas enters the EU it wont be Turkeys problem... make that clear in the agreements... any stealing gas is not Turkeys problem.... Gas can be negotiated for all of the EU and pumped... what the EU countries do with it then is not Turkeys problem.
Or they could stick to their guns and just hang on to Idlib and keep a war torn shit hole that will never develop and grow... it will just be a war torn Afghanistan like sht hole, where groups can get armed and trained and radicalised... and of course maintain hostile relations with Assad with his new improved military and of course a hostile Russia.
That would probably also blow the S-400 deal too, but America will be happy... or is Trump the sort to bear a grudge and look forward to the economic problems looming for Turkey... in the hope that they can have another go of getting Erdogan into prison and their own puppet into power...
Perhaps Erdogans best chance is a mega loan from China and some financial support from Russia to get them through this... they make parts for the F-35 and have some very high technology capabilities... perhaps they... I was going to suggest getting together with India to develop an export oriented Su-57, but I doubt they want to wait that long or talk that much, so perhaps a Turkish Su-30MKI variant of the Su-57... where the bits Russia is not ready to export yet could be French or Turkish... and of course anything the Turks want to add could be put in the mix too... their might be interest from some EU nations who don't want to spend 100 million an F-35... Su-57MKT.
OK... a little off topic... but important considerations for Russia in Syria too...
Remember Putin has to come up with new counters to all these sanctions the US has been imposing, and he doesn't want to hurt Russian interests... so for example banning the sale of rocket engines to the US only makes sense if there is an alternative customer to buy them... So Iran and North Korea spring to mind...
But what could he do regarding Turkey where Russia is not penalised but the US is pissed off?