Ragnar Frisch in the early 1960’s had high hopes for future Soviet economic development:
The blinkers will fall once and for all at the end of the 1960s (perhaps before). At this time the Soviets will have surpassed the US in industrial production. But then it will be too late for the West to see the truth. (Frisch 1961a)
That is from an article by Sæther and Eriksen in the new Econ Journal Watch. The paper contains much more than this angle.
It must be said that it was quite common for economists at the time to believe that the Soviet Union had a sustainable system. For instance Paul Samuelson, who repeatedly pushed his predictions for when the American GNP would be overtaken by the Soviet GNP further into the future. If anyone knows about any modern Norwegian debate about this, I would be interested to learn about it.
H/t: MR, Arnold Kling.