If Toyota has a bad '09, then count on them being engine supplier for Williams exclusively.
However, I think they'll go quite well this year, and as such, expect to see them through to the end of 2010/2011. I see this scenario as possible for 2011/2012 though, Toyota becoming engine supplies/Title sponsor to Williams, maybe with the Lexus brand and Black/Gold livery, seeing as Williams should be regularly competing for the championship by then
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