Only needs to be 492.13' to make it a skyscraper.
With >30% office vacancy and the future of needing office space seemingly less relevant as tech marches forward it seems unlikely. Of course things could change in a decade but kinda pessimistic on the super expensive skyscraper office, even worldwide.
So my vote is 10 to 15 with Unlikely as an option since Never is .......well.....forever.