I think every team has faced one difficult moment or the other and bounce back to better way and everyone expects Barcelona to come back stronger next season since they finished the league as runners up and trophies in all competitions, they have to try and get better next season since they had already changed their manager and brought in a new one.
Barcelona suffered a lot of set backs this season but they were able to still be at the top after Real Madrid and despite not winning the league because Real Madrid was already ahead of them with many points they finished ahead of Girona who was dragging the position with Real Madrid at the start of the season. Barcelona will not remain in poor form by next season and I don't see Girona taking the place of Barcelona in the league any time soon because Barcelona still has a better team and more quality players then them and for next season I think the competition will be tough because notable players may be joining the team in the transfer windows.
It's true, ups and downs in performance definitely come to every team, and that is a very natural thing to happen. Barcelona setback this season is actually not significant, with a limited budget to build squad depth, Xavi was still able to bring Barcelona to finish in runnerup position. It is not an easy job to compete with Real Madrid who have a stable financial condition, and Xavi cannot be entirely blamed for Barcelona failure to retain the trophy. Next season Real Madrid will continue to lead the competition for trophies, therefore Barcelona needs to work hard to build better squad depth, even though we realize that Barcelona is currently hit by a financial crisis.
Whoever will be Barcelona coach next season, in my opinion it will be very difficult to compete with Real Madrid, especially if Mbappe manages to land at Santiago Bernabeu. It is very likely that Barcelona management will again deal with a number of player transfers with loan options, or by recruiting free agent players as usual, with the aim of getting around the financial difficulties they are facing. Releasing young players could be another option, and Barcelona could recruit more experienced players to look forward to next season which will definitely be much more competitive.