Asked when the decision on the line-up would be made, team principal Wolff replied: "Somewhere in the winter, I think but I don't know if it is December, January, or February."
When pressed on whether he would genuinely hold tight until then, Wolff insisted: "[It is] highly possible because we have always been committed and loyal to the drivers and this is what we are doing."
On what Bottas has to do to remain with Mercedes beyond the end of the campaign, the Austrian added: "Drive cars fast on Saturday and Sunday. If he does that, he puts himself in a very good situation for next year."
Mercedes seeking consistent performance
If Russell was promoted, it would break a winning combination that has been together since the beginning of the 2017 season.
When put to him that there is an argument of adding fresh impetus from a new face in the team, Wolff said: "That is one of the components of all of the things that need to be considered, absolutely, but it is not the main driver.
"The main driver is consistent performance. Every team is going to judge that and especially in this difficult year we need two drivers that are racing right there.
"If one is having an off weekend or DNFs, you need the other to bring it home. That is why it is always important that both are on the max of their ability."
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