The AK-47 as it was adopted in 1947 was not the same thing we have today. At the time it was much more expensive to manufacture and not nearly as reliable. Much like the AR-15 it went through a long process of refinement (Stamped reciever instead of milled etc). The version that gave the AK it's reputation was the 1959 AKM variant. So in short an equivalent rifle would have been adopted and gone through the same process.
As for the SKS, the action wasn't much suited to full auto, which would result in trials of another rifle. The need for such a rifle was what prompted the development and adoption of the AK, not the other way around.
As an aside, the Yugo SKS is regarded as one of the more Subpar SKS rifle production variants. E-ger, polish, Russian, Chinese and Romanian are generally considered superior as yugo either has a very unwieldy riflegrenade attachment or lacks a chromed barrel, it is also generally more prone to corrosion. It is however one of the most available ones.