You often hear these days that Estuary English is "taking over" in the UK. I think this is overplayed. We have a few very visible TV personalities at the moment who speak EE - Jonathon Ross, Jamie Oliver, Robert Elms etc, and it seems to be a "trendy" accent in the media, but I don't notice it becoming a widespread way of talking throughout the UK - I live in the north east and regularly visit family in the midlands. The Manchester accent was all the rage a few years ago, but we're not all saying "mad fe'rit" now.
There is possibly a slight "converging" of Brtish accents - inevitable with national media, but I don't think they're converging into EE. Regional accents will go on for a long time yet.