This season, the big clubs in Europe have tried to take him with a lot of interest, but if he does not show such performance in the next season, then the big clubs will not show much interest in taking him.
Impressive performances in big tournaments like World Cup, Euro, and Coppa America can help many young players to become more famous and attractive to big clubs. Success in Euro 2024 with Spain actually helps Nico Williams to gain more interests from big clubs in the Europe.
Nico Williams has been offered by many clubs and if he accepts the offer now he can sign a long-term deal with those clubs and not have to worry about his career. If he decides to stay in Bilbao, he must improve his performance and play the whole season.
It's like a gamble because if he can improve his performance, he may receive offers from top clubs, but if his performance is worse than at present, his demand will decrease. There is still enough time so hopefully he will make the decision that is best for his career.
Bilbao will not be able to keep Williams for a long time and is facing with pressure from big clubs this summer. If they won't lose Williams this summer, they will lose him in future like next one, two or three seasons. Because Bilbao is a small club and in modern football, most of players are not loyal with a single club. They will move to bigger clubs to have better income from salary, shirt sales, advertisement rights and have better opportunities to win trophies.