Same thing that happened to peak oil? When people are screaming about it from the rooftops about one doom or another and whatever "it" is can't even stop a single year of human population growth (let alone decreasing it in a year) then the entire boy who cried wolf routine comes into play. It isn't that is isn't happenining...it just isn't noticeable enough for all the caterwauling going on.
Good news for the UK, the slowdown of AMOC should turn global warming into global cooling for the island...so good for the island remnants of Empire! Long Live The King! Etc etc.
Parts of America are going to suck of course, the slowing of the AMOC won't be an advantage to the US in any way, and probably a few other countries as well.