Sir Frank and Patrick won't bow down to whatever multi-million dollar car manufacturer tries to buy them out, that's one of the main reasons they fell out with BMW apart from dwindling results.
I think the Toyota engine's pretty good, Wurz and Rosberg were fast through the speed traps at quite a lot of the races this season, it's just the clowns at the Toyota works team who don't know how to use it right or know how to build a decent chassis (or make it look any different to the previous car).
Every team has its bad lull, did anyone predict Ferrari would come back to the front during their miserable pre-Todt/Brawn/Schumacher days - especially 1992? Lulls have come in batches of 4 years for Ferrari and McLaren, it took Ferrari 4 years from Alain Prost's win at Jerez in 1990 to win another race when Gerhard Berger won at Hockenheim in 1994. Likewise with McLaren, it was 4 years from Senna's last win at Adelaide 1993 to Coulthard's with in Melbourne 1997. As for Williams? Their last win to date is Montoya in 2004. Almost 4 years have past, so will there be a win on the cards for Nico and Kazuki in 2008?
People go on about the dominance of manufacturers these days, but answer this question... how many wins do Honda have? One. How many wins do Toyota have? A big fat zero... and don't forget Toyota finished well behind Williams in the constructors championship. Super Aguri also came close to scalping Honda, just falling short thanks to Button's wet weather skills in China, and the "2006 Honda chassis" used by Super Aguri having run out of room for development.
The moral of the story kids is no matter what big manufacturer you are, throwing money at everything won't bring results, not without hard graft and commitment. 
Add to that Williams themselfes have had a recent lull of 4 years, 1997 to 2001 between Jacques Villeneuve winning at the Nürburgring to Ralf Schumacher winning at Imola.
It has happened before and they could well pull themselfes out if this rut, although I think it will take a few more years to do so.