McIlorum, 28, went off on a stretcher after a tackle on Broncos half-back Anthony Milford and went to hospital.
The Leeds-born England international has played 220 games for the Warriors.
"Micky could be out for six months," Wigan coach Shaun Wane told BBC Radio 5 live sports extra. "He's playing rugby league and these things happen."
Wigan hooker Michael McIlorum is facing a six-month lay-off after sustaining a suspected broken ankle in Saturday's World Club Series defeat by Brisbane.