The German marque are joining Formula E as a full manufacturer entrant next season, taking complete control of their affiliated HWA outfit after a challenging debut season.
Vandoorne and Paffett have both been driving for HWA during the current campaign and have also conducted testing in the new Mercedes machine, with the duo operating under the assumption they will be in the car for 2019/20.
However, Mercedes are still considering a number of other candidates for the race seats and could overlook both current incumbents, with alternatve drivers set to test the new car later this year.
When asked about their driver line-up, Mercedes-Benz EQ Formula E Team Managing Director Ian James said: “It’s still to be decided.
“HWA have had a great rookie season and I think both Stoffel and Gary have done brilliantly well. They’re the obvious names that come up but we’re not going to make any firm decisions and nor do we need to at this stage.
“We’re going to launch the team in early September at the IAA [International Motor Show] in Frankfurt and I’d like to hope by that stage that we’re closer to confirming the driver line-up but it’s too early to say at the moment.”
Vandoorne, Paffett and Venturi driver Edoardo Mortara have all taken part in testing sessions for the new car, with the latter a Mercedes driver boasting vast experience alongside the manufacturer in sportscar racing.
Mortara is already signed up with Venturi for 2019/20, but James hinted other names could be in the frame and will test the car in the near future.
Vandoorne has impressed since joining the Formula E grid from McLaren at the start of the current campaign, and the Belgian believes he has done enough to retain his seat next season.
Speaking exclusively to Express Sport, Vandoorne said: “We’ve started this year as completely new team with zero experience in the championship and we’ve come a long way already.
“I’ve had a pole position in Hong Kong, a podium in Rome and feel like I have been able to push the team forward in the right direction. But there is still a lot more to come.
“I feel with Mercedes coming in next year that will be a big boost for everybody so it would be nice to have that continuity after having laid the base for the team.
“We’ve got to set the bar high for ourselves, and I want to be fighting for victories, fighting for championships and that’s what I target with Mercedes.”
Meanwhile, Paffett has strong ties with Mercedes after two titles across 15 years in DTM with the German giants and also hopes to stay put.
“I love the series, I love racing the car and I like being part of the championship so for me as long as I can get to the point where I can be competitive for the team then I would love to stay around for a few years,” said Paffett.
“My view, and what has been the view, is that we [Paffett and Vandoorne] will be staying together with the team and continuing through.
“It was initially a two-year plan to build the team and go into Mercedes next year and for me that is still the plan and still what we’re trying to do. We’ve been testing the car together as well so for me that is still what is happening.
“But the nature of motorsport being unpredictable is that you never know 100 per cent.”