I really hope TOTAL gets lucky here and that this thing seals itself off as you predict. That, however, does NOT equate to all being OK with the safety of hydrocarbon production in general. It seems like the accident frequency is increasing.
The problem with North Sea incident reporting is they report absolutely everything as an incident....from the tool man knocking over a can containing a quarter litre of diesel that sits on the topside deck to something like the Total incident. The number of serious incidents are not increasing in proportion to the number of wells drilled. To the contrary the safety requirements that the British regulatory body has put in place have resulted in fewer serious incidents.
I read a note from Total yesterday that indicates the source of the gas leak is not from the formation they are producing in but rather from a zone hundreds of metres above it where it was not known that gas existed. The most likely scenario in my view now is that the casing over that upper zone developed a channel in the cement bond between the rock and the casing allowing gas to escape into the annulus above. If this were the case the operator should have seen anomalously large annular pressure when they investigated the wellhead to abandon the well. In any event Total suggests this is a small pocket of gas and given the rate seems to be decreasing this seems to be likely. As to whether a top kill will work or not it is impossible to even guess at that until such time as they can inspect the well head. The last I read they were trying to send out a robot submersible to have a look.