Romelu Lukaku has a serious injury and he will stay out of the fields for months. He will not have a surgery but he cannot return before at least another month if not couple of months.
His team will have to deal with his absence for quite long time so unless they do very well in the first matches, they will be in hurry to find a suitable replacement
Lukaku has a severe injury and now he has two options: a surgery to solve this injury entirely and it takes him about 5 months for recovery; and a temporary treatment that takes him about 1 or 2 months but later reinjured risk is not too small. Next summer, World Cup 2026 tournamnet will be like a last big tournament for Lukaku with his Belgium national team and this tournament makes him very hard to choose how to solve this severe injury.
Taking a surgery or not, there are different times of recovery as well as different risk of reinjuries and probability of missing World Cup 2026. Lukaku is definitely aware that this coming World Cup tournament will very likely his last tournament with Belgium national team.