I personally don't see it happening. I didn't really consider the profit argument, but I'll take your word on that. I personally don't think E3 would affect profits at all. I think they can still do directs and show other footage and stuff prior to release if they want. But maybe you're right? I think the other thing is just that a lot of AAA developers are putting out less, and it takes longer, and they just don't have a ton to show every single year.
I think they miss out on the spectacle, the cross promotion, the ability to see interviews and fun and make celebrities out of more developers and directors. People are big on community and big on transparency. They can see every aspect of the lives of influencers they follow and gaming is still in this dinosaur secretive mindset. E3 could be a place to meet people, showcase people, showcase games, talk to creators, all of that. But I doubt it will ever happen.