(something) is anyone's guess

no one knows the answer.

How the lawsuit will turn out is anybody's guess.

At that point, whether he was dead or alive was anyone's guess.

• a grab bag
• a grain of truth
• a grass widow
• a greasy spoon
• a great deal
• a great deal of
• a great deal of something
• agree to disagree
• a grey area
• a grin like a Cheshire cat
• a guiding light
• a guiding spirit
• a guilt trip
• a guinea pig
• a gut-bucket
• a gut feeling
• a gut reaction
• a hair out of place
• a hair's breadth
• a hair shirt
• a halfway house
• a half-wit
• a hand-me-down
• a hanger-on
• a hang-up