I agree, we should consider that further oxygen loss could come from long burning wild fires etc, should the environment lend itself to a higher propensity to them. This could both burn oxygen and remove plants that would therefore not create and replace oxygen (in the short terms at least).

I am sure there are some weird feedback loops we are going to see in the next century or two, that aren't yet considered an issue.

We're quite likely to start running out of fossil fuels in the next few decades. It is unlikely that the loss will accelerate.

To play devil's advocate: Nothing suggests the trend will accelerate. It is just as likely to decelerate.