Sauber says that Audi will have no presence on its rebranded Formula 1 car next year, but insists there is no watering down of its works plans for 2026.
"Commercially speaking, it is important to have a big bang in 2026, not to dilute the Audi involvement with the team. So, we will continue as Sauber, based on the heritage of the group."
I guess that's a...reason. Reading between the lines it seems like Audi doesn't want their name on a backmarker, or, there is some hesitation on their F1 commitment.
I think Audi only want their name on the car if it has their engine in it. Also I'm not sure how much Audi is going to take over Sauber engineering on the chassis side in 2026.