A summer of change is on the cards at a Ligue 1 club with a collection of highly-rated youngsters at their disposal.
Ferland Mendy has already departed for Real Madrid, while Nabil Fekir is once again attracting interest.
Moussa Dembele and Houssem Aouar have also generated transfer talk, with clubs across Europe monitoring their progress.
Ndombele could, however, be the next to head for the exits, with Aulas conceding that contingency plans are being drawn up for the possibility of the France international moving on.
He told reporters when asked for an update on the latest rumours: “We don't have to sell, but if there's a big offer the door isn't closed.
“If Tanguy Ndombele has to leave, we'll target new players and Thiago Mendes is one of those players that interests our recruitment team.
“Tanguy Ndombele is pragmatic, he did not say: 'tomorrow I'm definitely leaving'. He has been followed by the big clubs and when they come in [for your players], you have to listen.”
Aulas added on the challenges facing Lyon as their most prized assets attract admiring glances: “We did the basics in terms of departures.
“We really need substantial proposals to move forward on Tanguy's future, which will eventually require him to leave.
“If he were to leave, which is not the case today, we should sign [a replacement] based on previous experience.
“For now nothing is done, but the door isn't closed.
“A deadline? No. We should not say that, but it's for good reason that we do not need any money until June 30 to present our accounts. If he wants to stay, I'll be happy.”
Ndombele has spent two seasons at Lyon, having initially joined them on loan from Amiens in 2017-18.
He has made 98 appearances for the club, recording four goals, and earned the first of his four senior caps for France in October 2018, having been drafted into Didier Deschamps’ plans on the back of a World Cup triumph for Les Bleus.