Sentence examples for theirs would be from inspiring English sources
The phrase 'theirs would be' is correct and usable in written English
It is used when you are referring to what another person or group is likely to do or have. For example, "He thought his team was the best but theirs would be the one to win the championship."
"That, in our view, as in theirs, would be enormously destabilizing, not to mention unbelievably expensive," he said.
I wrote a long time ago about how all these little projects of theirs would be connected and unified, the way the Romans unified their empire by joining all the little roads to their big roads.
Theirs would be a very difficult case, Hughes had told them.
Early on they agreed that theirs would be a childless marriage.
And if she were to do so, she wanted assurances from Sergeant Rossman that theirs would be a complete relationship.
They had seen the superintendent's home, and knew theirs would be renovated in a similar style, so they weren't worried.
And, importantly, services at least paid lip service to the idea that data was "ours," not "theirs," and would be treated accordingly.
She knew that until women occupied the spaces men had always called solely theirs, it would be hard to argue we were "just choosing" to become homemakers or nurses or other helping professions.
I gave some thought to finding a way to make the evening feel festive, no easy feat when small children, theirs and ours, would be underfoot well into the night.
Democrats had only to maintain their composure and the White House would be theirs.
The cultural capital that their parents had hoped would be theirs was elusive.
