Although Lewandowski has reached an agreement with Barcelona to stay with Barcelona until the end of the season or one more season. But Barcelona must move quickly to find a replacement, Barcelona is currently eyeing Newcastle United striker, Alexander Isak, and Viktor Gyokeres from Sporting CP is a more affordable option with a cheaper transfer value.
Barcelona management will not take the risk too quickly to find a replacement for Lewandowski in a financial condition like this. As long as Lewandowski can still be relied on, Barcelona management will look for a replacement player with an easier option such as a player who has free agent status. And in my opinion if Barcelona is eyeing Alexander Isak, it is just a rumor. On the one hand, Newcastle will not release the player at a cheap price and while Newcastle currently still needs the player. So at this time Barcelona can only survive with the existing players and look for a replacement player slowly without rushing which can put more pressure on Barcelona's finances.
One season is not a long time, it is a very short time to pass, so Barcelona must move quickly to find another player who can replace this striker. If they do not move quickly, then they will be left behind, I mean they will be confused when they are really left by Lewandowski. This should be a very basic thing, where they must quickly prepare a replacement player when one of their players is predicted to not be long in the team. Many teams ignore something like this, so after they really leave the team is very confused.
I don't think they need to rush right now. Lewandowski is still performing very well and I think he can play for Barcelona for at least another year. Also, if Lewandowski leaves Barcelona, Barcelona will definitely find a striker in the summer. Barcelona will never be without a striker. As I said, I think Lewandowski will play for Barcelona for another year.