During this transfer window, many rumors speculated that Barcelona would welcome Messi or Neymar back. But in reality, nothing unexpected happened. Their economy needs to be more vital to do that. Focusing on young players remains Xavi's top priority.
On the other hand, Xavi expects the squad to remain the same as last season when they successfully won the La Liga championship. Lewandowski will undoubtedly be an indispensable part of Barcelona. Still, if he loses form this season, this is a sign that Barcelona needs to spend a lot of money to find a striker to replace him.
Both Messi and Neymar are always looking for money, they don't care about their previous teams that make them to reach to their current position, only Ronaldo is still want to play in his old team.
Xavi is nothing to worry, they have Joao Felix that can replace Lewandowski and sooner or later the young star e.g. Vitor Roque will become a striker in Barcelona.
I don't understand why you say Messi is greedy for money. He agreed to take a pay cut to stay in Barcelona and returned there. Barcelona pushed him away and did not agree to let him return to Camp Nou. Messi chose to join Inter Miami instead of receiving a more significant amount of money from Saudi Arabia. He wants to find a new home at the end of his career.
Meanwhile, Ronaldo was the one who needed money when he agreed to go to Saudi Arabia.
Do you think football is really that simple? The way you want to change a central striker is straightforward.