I have been sceptical of Grealish's ability to play in a Guardiola side but there is a rational argument for why it won't be a surprise to see Grealish come good next season. I remember an interview with him where he said that Pep and the staff were showing him stats where he has been a leading player this season and therefore why his modest headline stats of goals and assists shouldn't worry him too much.
The tweet below shows how he's been in the top 10% in Europe for both link up play and threat creation.
The link below shows that his expected assist numbers are in the 97th percentile for the league this season whilst his actual assists are in the 40th. This means that while he's one of the best in the league at creating goalscoring chances the players that he is creating for have underperformed. His xA would only give him 2 more assists with the minutes he's played but projected across a full season it would give him 10 which would put him joint 3rd in overall total this year. The report also shows how he top the stats with progression, passing and shot creating actions.
The big negatives are his finishing and defensive stats.
https://fbref.com/en/players/b0b4fd3e/scout/11160/Jack-Grealish-Scouting-Report