Warburton led Wales throughout the 2011 Rugby World Cup after Scarlets star Rees was ruled out with a neck injury.
"I've had no indication what's going to happen, but Matthew was captain for the last Six Nations campaign," Warburton said.
"He did a brilliant job and it was only bad luck why he didn't end up being captain in the World Cup.
"So if I did it as a temp thing then I completely understand that."
Rees returned to Test action in December when he came on as a replacement during Wales's 24-18 loss to Australia in Cardiff.