Local media have reported that the exciting Spanish international could become the Barcelona squad's highest-paid player if he meets certain performance-related clauses.
The veteran Polish forward, 36, reached 27 league goals for the season, although he finished behind Real Madrid's Kylian Mbappe on 31.
The win comes against a mighty Barcelona team considered on paper to be the best in the world.
The Brazilian, whose previous deal was set to expire in 2027, was vital as Barcelona won a domestic treble of La Liga, the Copa del Rey and the Spanish Super Cup.
Villarreal qualified for next season's Champions League with an entertaining 3-2 win at newly-crowned La Liga champions Barcelona on Sunday.
Barcelona's 28th Spanish league title caps a remarkable season defined by teenage sensation Lamine Yamal, who at 17 has emerged as world football's most electrifying talent.
A stunning Lamine Yamal strike helped crown Barcelona LaLiga champions with a 2-0 win at local rivals Espanyol on Thursday, with victory ensuring Real Madrid cannot catch them at the top of the table.
Defending champions Real Madrid may well lose the LaLiga title race to archrivals Barcelona tonight, but Los Blancos were happy to keep the fight alive for another day with a last-gasp 2-1 home win over Mallorca on Wednesday.
Real Madrid snatched a last-gasp 2-1 win over Real Mallorca on Wednesday to delay Barcelona's title celebrations.
Real Madrid said complaints made by Copa del Rey final referees against pressure from the club's television channel were 'unacceptable' on Friday, after pulling out of planned pre-match activities.
Real Madrid refused to partake in planned Copa del Rey final related activities on Friday because they were angry at complaints made by the match officials earlier in the day, the club told media in Seville.
Arda Guler struck the only goal as Real Madrid won 1-0 at Getafe on Wednesday to claw back to within four points of LaLiga leaders Barcelona.
Barcelona inched closer to the LaLiga title with a 1-0 win over Mallorca on Tuesday which took them seven points clear of Real Madrid.
Flick said it was one of those comebacks that nobody forgets easily, adding it was not easy to win after Borja Iglesias netted a hat-trick to give Celta a 3-1 lead.
Barcelona will be aiming to open up a seven-point lead at the top of LaLiga table when they welcome Europe-chasing Celta Vigo on Saturday.
Barcelona coach Hansi Flick on Friday demanded to meet with La Liga officials over what he called a "joke" schedule, saying Spanish football was failing to take care of players.
Barcelona are through to the Champions League semi-finals with a 5-3 aggregate win, despite losing 3-1 at Borussia Dortmund on Tuesday with Serhou Guirassy hitting a hattrick.
Flick's side, undefeated in 24 games across all competitions, are not taking Dortmund for granted despite carrying a 4-0 advantage into the return at Signal Iduna Park.
Trailing 4-0 going into Tuesday's Champions League quarter-final return home leg against Barcelona, Borussia Dortmund coach Niko Kovac said his side can draw inspiration from Liverpool's 2018-19 comeback against the same opponents.
