The news came as a surprise when Rosenqvist was seen as the heir to five-time winner Scott Dixon in the long-established top team.
The New Zealander who will most likely take home a sixth title in the final in St.Petersburg, Florida, the last weekend in October.
Felix now has to replace the Swedish-American Oliver Askew in the new team.
He gets strong Mexican Pato O´Ward, fifth in the championship, as a teammate, writes motorsport.com further.
High expectations
Rosenqvist became this year's newcomer last season and expectations were high for the Swede for this year's season.
He took his first victory in the series, but the year has also been fraught with several failures.
Before the final competition, Felix is in a modest tenth place in the summary.
There is much to suggest that Dixon will continue on his contract with Chip Ganassi over 2021. According to motorsport.com, Marcus Ericsson will most likely remain in the team and that NASCAR star Jimmie Johnson will drive a third car on the traditional racetracks and city races.
Here it is speculated that Tony Kanaan drives the oval race for the team in the third car.
The Brazilian officially ended his career during the season.
CLIP: Felix Rosenqvist took a historic victory (July 13, 2020)
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Historical victory for Felix Rosenqvist.
Photo: TT News Agency / Viasat