Dembele's contract at Barcelona is due to expire at the end of June, meaning that Sunday's clash with Villarreal could be his final game for the Catalan outfit.
However, Xavi remains "optimistic" that an agreement can be reached over an extension, with the two parties expected to sit down after the contest with the Yellow Submarine.
"It could be (Dembele's final game against Villarreal), as for other players too... but he could also renew. He's a decisive player. I really like him, I'm optimistic: I hope Ousmane will continue here at Barca," Xavi told reporters.
Barcelona president Joan Laporta recently said that the club had submitted a new offer to the France international "a long time ago" but were yet to hear back.
"The offer was presented a long time ago and they have taken time to answer us," Laporta told Catalunya Radio. "We cannot force anything because this depends on two parties.
"I believe that he will stay, but he is tempted by other options that he could believe are superior."
The 25-year-old has represented Xavi's side on 31 occasions this season, scoring twice and providing 13 assists, including one goal and 13 assists in 20 La Liga outings.
A number of clubs, including Paris Saint-Germain, Chelsea and Manchester United, continue to be linked with the World Cup winner, who moved to Camp Nou from Borussia Dortmund in August 2017.
The forward has struggled with a number of injury problems over the last five years but has still made 149 appearances for the Catalan outfit, contributing 32 goals and 34 assists in the process.
Having been an unused substitute against Getafe in the league last weekend, Dembele will be bidding to return to the starting side against Villarreal on Saturday night.
Meanwhile, Xavi also discussed Lewandowski during Saturday's press conference, revealing that the Poland international is "one of the options" for the club this summer.
"Lewandowski? He's one of the options, one of the possibilities. There are negotiations, he has one year of his contract left... it won't be easy. Financial situation? Laporta told me we'll be able to reinforce the team, there's confidence," the former midfielder told reporters.
The 33-year-old's contract at Allianz Arena is due to expire next June, and he recently said that he wants to leave the German champions this summer.
Lewandowski has enjoyed another impressive campaign at club level, scoring 50 goals and registering seven assists in 46 appearances in all competitions.
The experienced forward's agent Pini Zahavi is in 'direct contact' with Barcelona over a move for his client, according to Italian journalist Fabrizio Romano, and he only wants to join the Catalan side this summer despite interest from other clubs.