The ETOPS requirements for fire suppression now apply to all passenger jets, regardless of the number of engines. In fact, nearly all the ETOPS requirements except engine reliability apply to passenger quads. It's been that way since around 2010 IIRC.
tdracer,
Is that all pax jets, or all newly certified pax jets? Our NB Airbii only have one bottle, with one shot, for two cargo compartments. I'm told that the probability of detecting smoke in both compartments on one flight is very low.