The Grove-based squad is evaluating whether Sargeant is making the necessary progress in his rookie season to justify being given another year in the car.
Although the American has shown some promising speed for the team, he has yet to score a point and has had a spate of accidents along the way.
Team boss James Vowles made it clear after another crash in Japan that he still had faith that Sargeant could step up enough, and that the scenario he was eyeing was them continuing together next year.
Asked at the Qatar GP about the time frame for making a call, Vowles insisted there was no rush and he was willing to give Sargeant every opportunity to show what he could do.
"I suspect it'll be to the end of the season," said Vowles. "I think we've already committed to the direction of travel we're in.
"He has targets to hit and it'd be wrong to go against that decision point. So end of the year."
Vowles explained that Williams was so willing to be patient with Sargeant because it saw the potential that the youngster was delivering – and all that it needed to see was him putting together more complete weekends.
"The pace is there," added Vowles. "That's the thing that we wouldn't be able to fix or repair.
Source: Autosport