I'm a little torn... I'd be lying if I didn't confess to feeling a little like joining in the omgsupertall!1!eleventy party, but from a skyline-wank perspective I dunno if I like the idea of the CBD getting upstaged by Yonge-Bloor.
Aside from the CN Tower offset to the southwest of the core, it just seems aesthetically "right" to me that the tallest towers be clumped more or less in the current pattern as the focal point of the skyline from 30 km away, with proportionate step-downs from FCP down through the rest of the Bay Street gang. The day probably will come where FCP gets out-heighted by some fresh omgsupertall!1!eleventy proposal, but ideally that should be by another downtown core location first, with FCP falling into line as the new beta dog and so on down the line.
I'm totally for a secondary cluster of height at Y-B, but to me, part of it being secondary is having it being at least 15-20% shorter than the main stage act to the south---in other words, ideally nothing past 250m at Y-B until something else is past 300m in the CBD.
I realize that sort of sentiment could, objectively, be seen as irrational cranky-old-man-type conservatism about things needing to be the way they are because the way things are is best. And, needless to say, the skyline from 30 km out isn't some master-planned portrait painted by a single artistic vision, but rather an emergent piece of art that's a sort of functionalist product of land-use policy and infrastructure placement and market conditions. If there is to be a 300+m residential tower built in Toronto, it could well be that the market says the financials would be easier with a Yorkville placement a la 1BE compared to being down in the financial district a la Trump.