I think McLaren will be fine, they have always been a collective of brilliant minds rather than one single figure sticking out.
Also, I don't think Mercedes will pull out. They are probably the manufacturer who is more involved in motorsports than any other (and by that I mean ALL manufacturers, not just the ones currently in F1; and yes, even Ferrari), it just doesn't make sense for them to not have a team in what is arguably the pinnacle of motorsport.