Possibly. However, high-volume customers tend to find bugs quickly if they are affected by them, especially those "happens once every couple of thousand hours on average" bugs.

If no high-volume customer has reported a particular bug yet, they're probably not affected by it (since they don't use that particular function/peripheral of the chip, for example), and engineering hours and the cost associated with producing a new revision spent on fixing it would essentially be wasted. Even worse, releasing a new revision of the chip might rouse suspicions.

Short version: The chip manufacturer probably accepts that there's no such thing as a completely bug-free chip, and will only fix those bugs that likely affect the majority (by volume) of its customers. Anything else is only fixed if it is inexpensive, or merely documented, or even ignored if deemed obscure enough.