Marko is serious about possible Red Bull departure: "This is not blackmail"

"This is not blackmail, this is a fact," said the Austrian to Auto Motor und Sport. "If there is no development freeze, we cannot implement the Honda project. With these complex engines, further development is not possible without a development center like Sakura. And that wouldn't be affordable either."

A freeze on engine development would therefore be the best option for Red Bull, but it seems unlikely that all manufacturers would agree to this at this point in time. If that doesn't work out, Red Bull would have to negotiate with Ferrari and Renault for a customer engine. 

Renault and Ferrari are not going to offer an easy solution either

"It all sounds simple, but it is not. You can imagine what would happen if we beat the factory team with a Ferrari engine. And Renault, too, has a new confidence that they can do anything with their new engine and Mr Alonso in 2022. If we do not agree, a departure is also an option. We have been realistic about that."