Unless "looking forward to the debates" is not a commitment, and maybe it isn't, in which case neither of them has committed.
I just think it would be insanely foolish for anyone on Trump's side to think they can win without a debate. Right now, he is running against an image of Biden, not the real Biden, and no one can beat a carefully crafted image. The Trump campaign needs a direct comparison to be made by voters. I don't think anyone is advising Trump to back out of the debates. Let me know if you find one.
And, it is questionable whether Biden will be able to manage 3 debates without getting very confused. Dementia is a weird thing. It comes and goes. And, maybe there are medications that can help him be lucid for short periods of time, I really don't know. But, right now, it is only Biden who takes a risk by debating.