Before you see that Pep Guardiola doesn't want to sell Gündoğan, it means Pep Guardiola still needs Gündoğan at Manchester City, and if Gündoğan's contract with Manchester City comes to an end, Manchester City can possibly extend his contract, which will allow Gündoğan to remain at Manchester City, so there's no need for you to get worried about Gündoğan leaving Manchester City for free when his contract with Manchester City comes to an end.
His contract still has one season left and I don't think it's a big concern because he performed quite well when he beat Al Ain in the Club World Cup.
Pep Guardiola does plan to streamline the squad but as long as Gündoğan is able to perform better, he will definitely get a place because Pep Guardiola himself really believes in his performance on the field.
Next season will be another matter, whether Gündoğan will leave or not because after his contract ends if the contract extension option is not exercised, perhaps Manchester City will consider Gündoğan is no longer a priority.