I would imagine the 40-player limitation comes from the fact that 64-player is absolute rubbish in Battlefield 3 and 4, the maps aren't and can't be designed for it - not if they're adamant that players shouldn't have to travel far between objectives. I never played a single 64-player game of BF3/4 that wasn't just a stalemate meat grinder set up just so that people could get a ton of kills for unlocks. 32-player games on the same size maps were still a bit like that, but you actually had room to move and use some tactics, when there are players in every corridor and every route is full of people, you can't really flank or dig in because there'll be another enemy you need to flank or you'll get shot in the back. 40 players is good for the size the maps will probably be (assuming they're Battlefield-sized), more players is not always good.
As for that video, sure it's in-engine but it's not real time. There's just no way.
No campaign? No problem, no-one on EA's payroll (outside of Bioware, at least) knows how to write a half-decent campaign. That's four hours less cringing for me, that's actually a win as far as I'm concerned.
DLC: This is EA, the people who are still trying to sell me BF4 kit unlock shortcuts even though I've already unlocked everything included in them. If you think EA are going to release a big-budget game without DLC you are sorely mistaken. They play it safe and they set everything they release up for serious milking, monetising everything short of controller layouts, graphics options and... Umm... But that's just the way the AAA industry is now. EA are certainly leading the way, though.