Barcelona couldn't extend with Messi due to financial issues, I am not sure if they will be able to afford extending contracts with all of these players.
All of them are young and will be interesting to other clubs and these clubs can start to officially negotiate with the players on January 1st - meaning that they already started negotiations in the background.
Pedri will extend - that's almost sure. But the other 2 will be hard to keep.
After the fans can return to support club in the stadium, the club's finances will slowly start to improve, they get money from ticket sales that could not be obtained last season. Indeed, money from ticket will not be much, at least the sponsors will also start thinking about marketing their products in Barcelona, even though there is no Messi, but they are still a big club.