The Electoral College will be abolished once a third party has established itself.
As soon as that happens each presidential election will get redirected to the House of Representatives, which will result in random winners.
Displeasure within the population will motivate the powers that be to rethink.
Except as long as the EC exists, we won't get a third party. We might get a new party that replaces one of the other two, but not a stable three party system.
You'd better take a look at the British election maps:
There you have a stable three party system,consisting of:
the Conservatives (Tories), the Labour Party (British spelling of "labor") and the Liberal Democrats. (plus some other small parties)
Once a third party enters the House of Representatives or even the Senate - it'll presumably be the Libertarians - it is talked about as a president-maker.