I don't think Barcelona is in too much of a crisis. If Barcelona does not buy a new striker this season, they will not face any problems. Barcelona's forward Lineup is still strong enough. And their gameplay is excellent. Their only weakness is defence. On the other hand, if Real Madrid cannot add any new talented striker, and if Benzema cannot maintain his form, then Real Madrid's performance will be severely reduced.
Xavi will probably earn some money which he can use to transfer new players in their preparations for next season. Barcelona's performance has been much better than before but of course they still need some improvements, especially in defense and attack. Ansu Fati, Aubameyang, Ferran Torres are still reliable next season but Barcelona still need more players than just them.
Memphis Depay, Luuk De Jong and Adama Traure are unlikely to play again at Barcelona next season because they are rumored to be sold or returned to their respective teams. So of course Barcelona need a replacement especially Barcelona will be eyeing the title next season.
Yeah they need to bring in some good strong players in defence that can hold their opponents. Need to work out a bit on attack and right now lot of reports are linking Lewandowski to Barca that will turn out good if that happens. Currently Bayern want Lewandowski to play until his contract expires which is next year and Lewandowski wants to move out so its a tough deal.
Meanwhile yeah Barcelona are reported to allow the bids for Memphis and might sell if a good bid arrives. Regarding Luuk de Jong and Adama Traore, they are both on loan so they are not gonna be in Barca next season unless Barca triggers the buy option which seems unlikely.