A total construction time of 65 months was once claimed, resulting in a completion in 2018.
http://kingdomtowerskyscraper.com/
(The start date of April 27th 2014 is correct).
But I think they are not gonna make "2018" happen...
I would eat my hat, if I had one!
(note: The above link is not the officlal KT website as far as I know.
Does anybody know if there is one?)