Measuring the CKM Matrix Element Vtb at DZero and CDF

I present measurements by the CDF collaboration of the Standard Model three generation CKM matrix element Vtb and of a special case extension with additional assumptions, using current Tevatron ttbar data. I then show how we can significantly improve the precision on Vtb and at the same time extend the measurement so it is not constrained by Standard Model assumptions, using single top production at the upgraded Tevatron.