What if it can't be stopped?

I am not a geologist by any means, but this is how I would envision an unchecked leak.

Because water is not replacing the oil, there would be a breaking point in which the sea floor collapses - opening the leak by an enormous amount. The volume of oil would increase exponentially in a few hours, maybe less.

By the time this happens, nearly all the world's oceans will have been affected to at least some extent. Underwater lakes will be decimated (Underwater lakes article - text and Youtube I think there are probably tons of ocean lakes, and they are probably fed fresh water from the gulf stream system. Once oil enters the lakes, it seems likely to collect and build up.

Some lakes will have massive die offs, probably some probably already have. Most affected lakes will not have massive die offs, but will have some pollution. As the gusher continues and grows in strength over time, the lakes will collect more oil and more will die. When the floor collapses, many lakes that were only suffering mildly will suffer massive die offs.

I have no idea how long it would take to collapse the floor. But even if the leak can't be capped, I would think it would be possible to drill and create a water pump to keep the floor from collapsing.