Well they're just your typical car-manufacturer team. Only Ferrari sets itself apart these days from the other true car-manufacturers as a fully committed F1 team.
It's clear to see, that if Merc don't start hitting the heights they want within the next few seasons, then they'll go the same way as BMW, Toyota, Honda and all those other failed teams whose real passion lay in making road-cars and who couldn't cope with the realities of F1 stopping them from gaining instant and continued success.
If the passion, commitment and understanding is not there from the big-wigs above, then the only door open to the team is the exit.
Funnily enough there was a rumour a couple weeks ago about Toyota returning to F1 but that one seems to have gone quiet now. Given their spending and lack of success previously I doubt Toyota will return in the near future.
I can't see BMW returning in the near future given the way they left pretty sharpish.
However, it'll be interesting to see how the new engine reg's pan out. That may attract more engine manufacturers. Then there is the economy to consider - I heard today that it looks like this is going to be a double dip recession. That'll be a major deciding factor with the company brass I think.