The Australian, who has just 12 months remaining on his current deal, has scored 12 goals for the Championship outfit this season.
However, as one of the highest earners at the Riverside, it is understood that he will be placed on the transfer list in the summer.
"We all know what the situation is, we all know that it will be another summer of question marks, stories and rumours about my future," he told the Evening Gazette.
"It was like that last summer, with everything up in the air and a lot of talk about if I was going, when I was going, where I was going. But look, I don't mind all the speculation. It doesn't bother me. I can't let it get to me or distract me. I just ignore it and get on with my job.
"I've already said that I'll sit down when the season is over and talk to the manager and the club about what's best for me and for everyone and we will take it from there."
McDonald has previously played for Celtic and Southampton.