The Barcelona president says the club will not prevent the midfielder from seeking a move elsewhere if he chooses to do so
The Spain star has become a club great since making making his debut in 1998, but at the age of 34 found himself out of favour at times under Gerardo Martino last season.
The nadir came when he was dropped for his side's unsuccessful title decider against Atletico Madrid, when a victory would have handed the Catalans the league title.
The midfielder has since been linked with a number of clubs, including Qatari side Al-Arabi, and the Barca chief has opened the door to him potentially leaving Camp Nou.
"He has spent many years in the first team and has earned the right to decide [whether or not to leave the club]. We will respect his decision," Bartomeu was quoted as saying in AS.
"The day he leaves, he will go down in history as the best [Barcelona] player [ever]. If he wants to stay with us, [we will be] delighted, if he wants to go we will help.
"Xavi will return here because he will be a great coach," he added.
Barca unveiled new signing Ivan Rakitic on Tuesday after he completed a reported €20 million move from Sevilla, with the midfielder's arrival casting further doubt over the future of Xavi.