i think as far as E3 getting cancelled goes, and the possibility of it ending in general, i think it's for the best. if you pay close enough attention to each E3 in recent years it seems like sony and nintendo don't want to put much interest in being out there live on stage. nintendo has their "nintendo direct" series where they're live in their own area, and sony dropped out of E3 last year.
and i can understand that after setting up all these props and backdrops for the place to show off new games that it could get tiresome. now that we have the internet and online streaming there's really no need for it anymore. E3 was a big thing back in the 90s and early 2000s, but with how far the internet has come in these years it would be good timing on their part to end it. let's not forget some of the embarrassing moments from the mid to late 2000s from E3 when nintendo attempted to show off the ds and wii hardware with wii music and nintendogs, and when microsoft had some lukewarm responses with the kinect. people still talk about moments like those to this day and i'm pretty sure it's left a pretty bad mental scar for the company.