A rather unforeseen, unprecedented move really and perhaps a key one at that.
At first thought, the immediate outcome becomes more of a demand for the Ruble almost instantaneously based on supply. Quite honestly, it makes you wonder why no one thought of that before. Perhaps there was a need for a "precipitator". It also parallels the process of oil trading which occurs in USD.
Which makes you wonder...rhetorically...What if Russia doubles down and starts demanding Rubles for OIL!? Not necessarily as a move meant to dethrone the dollar's current status but one done in an effort to simply challenge the current status-quo. And then what if other oil producing countries begin to accept payment in currencies other than dollars? KSA and China have had preliminary talks about it.
