Is a war between Russia and Nato still a relevant scenario?

Yes it is. If Iran continues with its nuclear weapons programme Israel will attack. Iran will counter attack and has also sworn to attack Israel's allies, notably America who are prepared to allow Israeli jets to fly over US controlled areas. The US will retaliate and will support Israel. The big problem here is that the Iranian nuclear plants are staffed largely by Russian workers and Russia are not going to sit by and watch their country folk get blitzed. The chances of it remaining non-nuclear are zero and so the question of who will be the winner is rather academic. Few of us will crawl out of it alive. The whole of the Muslim middle east and Russia will support Iran. Iran is the second largest oil producer after Saudi Arabia and so Oil would shoot to over $400 a barrel creating a world wide fuel crisis that would plunge us into deep depression and fuel riots. Not a pretty picture.