One media source reported from Brazil that while Pierre Gasly is definitely set to drive for the junior Red Bull team next year, a similar deal for New Zealander and sports car champion Hartley is not quite done.
However, Toro Rosso team boss Franz Tost admitted: "There is a high possibility that this will be the driver lineup for 2018."
To put that deal beyond doubt, Hartley's father Bryan is set to travel to Abu Dhabi for the 2017 Formula 1 finale in two weeks.
"Once we all find out what's going on and there's something to be announced, then there will be an official announcement," Hartley snr told New Zealand media source Stuff.
Hartley finished 13th in the United States Grand Prix but was forced to retire in both Mexico and Brazil.