The club president said losing his side's La Liga title did not represent the end of an era but made it clear there will be significant alterations over the summer
Barca needed to beat Atletico Madrid to claim the Primera Division title, but could only draw 1-1 at home to Diego Simeone's side, meaning they finish the campaign with only the Spanish Supercopa to their name.
After the game, coach Gerardo Martino confirmed he would be leaving Camp Nou with immediate effect, with Luis Enrique lined up to replace the Argentine.
And Bartomeu revealed further changes were just around the corner.
"Now comes a time for deep changes," the Barca president said after the game. "Sunday will be a day of reflection and on Monday we'll meet and make decisions.
"There are many things we have already decided and we'll start announcing our decisions soon."
Bartomeu said he understands the frustrations of socios after the Catalans failed to end the season with a major trophy.
"I understand the disappointment of the socios," he said. "They are right. We haven't achieved the objectives we set. But I'd also say that we have a very good team and in a season with many problems, we have kept fighting until the end.
"Barca have very good young players who will give us a lot. This won't be a revolution, but a big renewal."
Finally, the Barca chief congratulated Atletico on their title triumph - their first since 1996.
"They have done really well throughout the year and against all the odds, they have beaten the favourites. We have to congratulate them," he said.