Vettel had been linked with the team to partner Lewis Hamilton after Ferrari announced he would be leaving at the end of the year, but Wolff insists that such a move is something the team owes to a four-time champion such as Vettel.
Wolff also said that while the move is only a rumour for the moment, more bizarre things have happened to the team in the past, such as Nico Rosberg's shock retirement from F1 after clinching the world championship in 2016.
"First of all, it's not lip service. I think we owe it to a four-time world champion not to come out and say straight away 'No.' You need to think about it," Wolff told Autosport.
"On the other side we have a fantastic line-up, and I'm happy with both our pilots and George. But you never know. One of them may decide that he doesn't want to go racing any more, and suddenly you have a vacant spot.
"And this is why I don't want to come out in June and say, 'No chance, Sebastian is not racing for us.' First of all, I wouldn't do to him as a driver, to be that blunt, and on the other side, I've seen black swans appearing when nobody expected.
"Remember Nico Rosberg. In that respect, we're just keeping our options open, but of course, concentrating our discussions with our current drivers."
Wolff also confirmed that there have not yet been any further talks with Lewis Hamilton over a possible contract extension for 2021 or beyond.
Hamilton, who joined the Mercedes team in 2013, where he has gone on to win five of his six world titles. finds himself out of contract alongside teammate Valtteri Bottas at the end of the year.
Despite being in contract with the reigning champion, Wolff has said that there has not yet been any further discussion on the matter but hopes talks can resume after racing gets underway in Austria on July 5.
"We didn't see each other lockdown, but we were in regular contact. But we didn't work on any agreement. Between us there is a lot of trust," Wolff added.
"We have been together for a long time, and never in these years together we had to take the contract out and actually read what was written in there because it comes so naturally.
"And therefore once racing resumes we're going to spend some time together, dig the contract out of the cupboard, look at the timings and the numbers and the rights and hopefully have something pretty soon."
Bahrain International Circuit - Winter testing