Actually i personally not so surprised about Newcastle being able to finish in the top four, because in fact Newcastle has very good progress and it has been seen at least from the previous season too, where Newcastle managed to avoid and stay away from the relegation zone. But yes, considering Newcastle will get a more solid schedule next season, then Newcastle should recruit top players and to prepare for the second player who also at least must have good quality too. Because if Newcastle do not prepare well in this transfer window, then i sure maybe Newcastle will be chaotic situation later for example failing in the Champions League but failing also to compete in the top four in the English Premier League.
I think newcastle united managed to take advantage of the imbalance of other teams last season so that they were really able to master every game consistently. By looking at the depth of the current squad, additional quality players are really needed because their schedule for next season will be more packed than last season. For now I think Newcastle United are strong enough looking at the depth of their squad but to compete in the Champions League they need to overhaul more aggressively the depth of their squad and bring in players who are full of experience in the Champions League.
Newcastle United still rely on Callum Wilson as their main sticker for next season because he returned to his best form last season. Moreover, Newcastle united has also managed to get Tonali who will be an additional strength for them to compete in the Champions league next season.
Callum Wilson has been amazing last season and i dont see a reason honestly to change him or get a new striker to replace him. For champions league they need new players but not on the striker position. Midfield and defence players are needed so they can at least pass the group.