be anyone's guess
US /bi ˈen.i.wʌnz ɡes/
UK /bi ˈen.i.wʌnz ɡes/

1.
zgaduj zgadula, nie wiadomo
to be impossible for anyone to know or predict
:
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When the new product will be released is anyone's guess.
Kiedy nowy produkt zostanie wydany, to zgaduj zgadula.
•
What he'll do next is anyone's guess.
Co zrobi dalej, to zgaduj zgadula.