The goalkeeper is yet to make a league appearance this season, with his outings being limited to cup competitions.
As a result, the 26-year-old may leave St Andrews to find regular starting action.
"I don't know. It's all up in the air at the moment. The club haven't spoken to me," he told the Birmingham Mail.
"But I'm 26 now, been here since I was 16 - I doubt if I'll get a testimonial! - and I want to be playing regular football. We will have to wait and see what happens in the summer, really.
"It's been hard. I've not had many games to play, but I've been behind some fantastic keepers here."
Doyle has had five loan spells during his career with the Blues.