dleung at SSP posted this a short time ago:
"Rumour has it that Casa IV is on the way at the parkade between Charles and Hayden. It will have the same wrap-around balcony design as Casa I, II, III and 1 Bloor. At 214m, it will be the 2nd tallest building north of College. Due to the subway occupying half the site, it will have Canada's second robotic parking garage (after Jameson House in Vancouver). Currently in schematic design - can release images in 2-3 months."
With that height, and assuming a similar floor-height as CASA III, it should end up with around 65 or 66 floors.