Great midfielder, the numbers and creativity on the pitch would speak for him, disciplined player, technically, smart and a modern player all of the top sides would want to join em if not for his age.
Money is not everything for every player, infact Barcelona deserves such a player and Gundogan also deserves representing Barcelona.
Xavi still needs a replacement for Sergio Busquet, he's not recruited a player for that position and also Gundogan won't be a great fit for that position if he was bought to replace Busquet. The name Joshua Kimmich have been mentioned severally, but the player have no plans and intentions to move to Barcelona.
Gundogan is a midfielder, he can play in place of Busquets. especially if we look at the available Barcelona players, but Xavi could have assigned him in another position, because he is a versatile player. he can be a playmaker, attacking or defensive midfielder. So the problem is, Barcelona needs mature players and Gundohan is the answer. don't be surprised, if he will partner with Do Jong as a pivot.
To be honest, I don't know what Xavi is planning in his project for next season. however, given the number of players who left. plus, which still survives. it is likely that he will fill the position left by the Barcelona captain. the question is, will Xavi change his tactical style and formation, most likely not. Barcelona will stick with its 4-3-3 formation. except, he studied what Pep implemented with his new system.
Speaking of Joshua Kimmich, if I'm not mistaken, the rumors are that Kimmich has blatantly refused that he will not leave for Barcelona. if they already have Gundohan, what else do they need. after all, there are second-tier players who are pretty good. but even then, if they don't include it in the sales list.