A few weeks ago, Kovacic was widely reported with Manchester City and he is expected to replace Gundogan if the Manchester City captain really leaves the Etihad Stadium next season. I think Kovacic is a good fit to fill Gundogan's position and with his experience it will be easier for him to work with Pep Guardiola. It seems that Kovacic's career will also increase if he is with Manchester City because it is very unfortunate if the talent he has to return to the same place with Chelsea.
It seems like that barcelona will be making an official announcement for gundogan after UCL final match. Some articles have confirmed that Barcelona has agreed with Gundogan to go to the club in summer.. Kovacic has been reaching agreement with manchester city.
You will able to see kovacic to replace gundogan very soon. Manchester just need to finalize the deal with gundogan at this moment. I think that you will be seeing kovacic to play in manchester city as soon as possible. The transfer fee for kovacic was not a problem for manchester city at this moment. City was a rich team that can pay everything as chelsea wants.
I wouldn't say Kovacic is a bad replacement for Gundogan. But I still have my doubts. I have followed up Kovacic right from his Real Madrid days when he was having little playing time. But when he went to Chelsea, his playing time increased But I didn't see his performance increase. That js why I am doubtful about him being able to replace the inform Gundogan.
However, when you are playing with a good team, as a good player, you will have no option than to adapt to the successful way of playing.