Chris Jenkins
Driving til the wheels fall off
It will be Mercedes, they have already said they had no issues with Mercedes having their own team.
Just like Renault had no problems supplying Red Bull despite them having their own works team.
I doubt McLaren will want to be the only top 4 team that has to pay for their engines.
As Luke said, Red Bull don't pay for their engines now that they're branding them as 'Infiniti'.