Instead of electric cars, use of alternate sources of energy like solar cars would affect the oil industry more and are more environment friendly ways of transportation. Affect on oil industry will affect the economy of few countries badly as they need to find alternate sources of income.
Yes, nowadays oil has more than one opponent although they all may decrease use of oil and also we cannot measure effect of one factor on oil.
It can surely affect on oil if electric cars really running on street well they lose big percentage of their income and thats great effect may ended to many people lose job and big percentage of world trade economy would be down, and iF realy happen those king oil countries will be suck and their economy will broke and alerted to be break down, and for sure government would not let it happen because they are making income with it in trades and surely they wil not let an ally in economy country will be down.
It will completely destroy the oil industry if cars are using electric to run, remember that the oil industry is a profitable industry for the big players in the market, if they lost that it is a big investment which they lost. To prevent that from happening, they will do anything to hinder the success of fully electric conversion of cars. It might even happen that they will bribe any government officials of any countries to let their personal interest happens at all time.