be anyone's guess
US /bi ˈen.i.wʌnz ɡes/
UK /bi ˈen.i.wʌnz ɡes/
1.
to be impossible for anyone to know or predict
:
•
When the new product will be released is anyone's guess.
•
What he'll do next is anyone's guess.
to be impossible for anyone to know or predict