It's certainly controversial.
Here's another article on the subject. Depends on what you mean by "oil" I guess. If the definition of "oil" is broadened sufficiently, the pollution might be eternal.
Are we nearing the idea of "virtual" pollution? Elements that are considered pollution even if they have no measurable effect on anything other than hypothetical future problems?
I don't know if studies were done prior to extensive Gulf oil exploitation (the first serious offshore oil work began sometime in the 1940s). I wouldn't mind knowing the "natural" levels of Gulf oil chemicals, or methane.
The NOAA press release here.