To be fair, the majors were almost completely absent from Broader downtown, (Lake to Bloor, Jarvis to Spadina) 20 years ago. In the interim Metro has added 3 locations, Loblaws has added 2, Longos added 1 full-size store and 3 mini stores, Sobeys added 1 full size (west side of Spadina) but 2 urban markets.
That said......have no fear, more are coming.
Within the tight zone (Front to Queen, University to Yonge) I'm only aware of 1 site under consideration.
But expand the range slightly, and I can tell you that 3 chains are looking at at least 5 sites; 3 are part of new-builds, two are re-purposings of existing space.
I doubt all of them will come to fruition in the near-term; but I expect at least 2 more in the next few years.
(many more than that if you stretch to the wider core (Parliament to Bathurst).( 4 more sites minimum).