The guys who run the British National Grid disagree that the grid needs major changes: http://fes.nationalgrid.com/media/1264/ev-myth-buster-v032.p..., http://fes.nationalgrid.com/media/1253/final-fes-2017-update.... The Norwegians aren't predicting the need for supergrid either: http://publikasjoner.nve.no/rapport/2017/rapport2017_77.pdf (sorry it's in Norwegian and too big for Google and Bing to translate).