Wouldn't the sentence technically translate to "In five years this castle will not exist anymore"?
Technically and what i know from duolingo, the sentence you quoted should be the most likely to be accepted.
Both your answer and "In five years this castle will no longer exist." are fine.
It should, but according to Duo it does not.
It is accepted as of now. (8/10/14)
'In 5 years this castle will exist no longer'? Why isn't this accepted?
I have the same question