Who'll

Who'll be taking over from Cynthia when she retires?

Who'll take care of the dog while we're gone?

Who'll get there the quickest?

I'll call a repairman I know who'll be at your house to fix the washing machine promptly.

Is it you who'll buy the food?

At that time, the city is full of people who'll either try to sell you drugs, steal your pizza, or ask you for change.

It's my dream to have a son who'll take over my business when I retire.

Who'll take over Cynthia's job when she retires?

If both Tom and Mary go to prison, who'll take care of their children?

You should probably tell Tom who'll be meeting him at the station.