I don’t see why Williams would want to get rid of either of them.
Money. Sad to say but Williams are not in the best financial condition at the moment. They are an independent team that needs to book profits for the owners and investor – so they do not have the benefit of backing from a manufacturer who can afford to sink in a big budget. They have also lost almost all of their high-profile sponsors in the past few years, and do not have the equivalent of what McLaren have with Vodafone, or Ferrari with Marlboro, holding up the bottom line.
BAR will be there next year, likely on less money, and the Hulk will probably need to either spend a year on loan at a lower team or will take a seat at Renault/Lotus. If Massa is ousted at Ferrari, there could be a merry-go-round that would see the Hulk get a better drive, but I don’t see it happening any other way (I think the chances of Massa not being at Ferrari next year are increasing each time he gets in the car)
If anyone needs to be booted the hell out of their seat, it’s Petrov.
He is alright, just give him another year. He might not ‘arrive’ in the same fashion that Hulk just did, but he is only an offseason plus a few more races away from being a good driver who can deliver points.