The only place WestJet has ever been "rumoured" is wishful thinking on this very thread. Yet another "GLA has it so EDI must too" wishful thinking "let's make up a rumour" type post.
WestJet won't be appearing at EDI anytime soon.
If there was demand for more Toronto then Air Canada would increase. They have been at EDI for what must be near a decade now and despite fares being rather cheap have actually reduced their EDI flights over the years, not increased.