Heres my two cents worth...
I believe that fuel along with priorities determined the Luftwaffe's fate. Afterall, a country with a limitied supply of fuel can not supply both land and air armies...
We must not let ourselves forget that the Luftwaffe was on the brink of achieving its goal over the RAF, but switched tactics (without knowing how close they were) and started bombing cities instead.
Could the Luftwaffe have achieved victory in the skies over Great Britain, if Germany had all the fuel she wanted and was not planning an invasion of the Soviet Union?
I think that Germany was capable.