Geoff Keighly has been trying to replace E3 with his Summer Games Fest. That’s where a lot of announcements come out. Iirc, Keighly said that this Gamescom wouldn’t be reveals for new games, but updates on ones we know are coming.

I’d say neither are really replacements for E3, since E3 had showcases from PS/Xbox/Nintendo. Nowadays all the major publishers and console makers have their own reveals.