Guardiola was quick to commit his future to the English champions after UEFA's announcement that they would be unable to take part in any European competition during the 2020-21 and 2021-22 campaigns - a decision Man City have appealed.
The Spaniard has never stayed at a club for longer than four years before - an anniversary which is approaching at Man City - and Petit believes that he could still decide to leave the club despite his comments to the contrary.
"I think that could be an option for him [quitting City in the summer due to the Champions League ban]. It could be an opportunity for him to step back and have some rest. It wasn't a long time ago that he seemed clearly tired of being manager," Petit told The Mirror.
"You never know what could happen, but for me the biggest worry is not what could happen if Guardiola leaves the club - there will be another manager coming if he leaves - for me the future of City is not linked with Guardiola forever.
"For me the main worry is what would happen to Manchester City if the ban is still on the table after the appeal. Everything that City has been doing for the past five, six, seven years, in terms of investment. Everything they have been building could be ending soon. It could change everything at the club. Top players want to play in top competitions."
Guardiola has won three League Cups, two Premier League titles and one FA Cup during his time in charge of Man City so far.