There are no maybes to it. This is how the Russian "nation" first came into existance. Although the "histories" of this time period are semi-mythological, it is clear that certain Scandinavian types who traded and travelled on the Volga river from the Baltic to the Black sea areas, eventually came to politically dominate the local population of utterly uncivilized and uncultured Slavs in the ninth century. Thus the first "Russians" came to emerge as an actual nation. First their kingdom came to be based in the Ukraine at Kiev. However, after infighting and trouble with steppe people that Kindgom eventually colapsed, but it's smaller brother principality centered around the trade city of Novgorod came to take their place as the Russian nation. With the arrival of the Mongols in the steppe areas of the Ukraine, the Russians were completely driven into the northern forests (areas where the Mongols had far more difficulty fighting) where they dwelt as a subject nation to the Golden Horde for about 200 years. This covers most of the period in MTW2. So in a long winded way -- the Rus were the founders of anything that today is referred to as Russian, since before their coming, the area was completely and utterly unimportant in the scope of world politics (and the root "rus" does indeed always refer back to these people).

P.S. My Russian history class was over 5 years ago, if I screwed up some minor details, I apologize :)