While these are very valid concerns, my understand is that the above grade portion of the project has not yet been approved for construction (which nowadays is more common), and this is a high level rumour to the point where the contractors are being asked to preplan a possible increase.Also, a change this drastic to increase the height would also mean slowing the construction down to account for any required additional structural analysis. I don't think they'd be able to forge ahead on building the basement if the height is being increased given that they might need additional support columns to support the extra weight of the new floors.
Also, the building bulges out and back in through the height of the tower, so any increase in height might also mean they have to change the super-structure to match the new height. With orders for the cladding and windows probably already locked in, they wouldn't risk jeopardizing that.
I will be super pumped if I'm proven wrong and it does happen, but with what we know currently, I'm not optimistic.