Some will say Days was a bad game, but how many casual fans have actually sat down and played Days? Not many I'd assume.
In fact, many. It was one of the highest selling 3rd party DS games in the United States back in the day. Well over a million units sold in America, so it wasn't just the core audience playing. I'd suspect that its poor reception was one of the reasons sales of Birth By Sleep in North America were average (along with the fact the PSP was a dead console in the west and piracy was rampant.)
KH3 is probably Square's best asset right now. It's got a crapload of hype and if the hype dies because of lack of updates, it will not end good for them.
The hype isn't going to die because Square Enix hasn't informed people what they are doing every single step of the way. Kingdom Hearts 3 generates hype on its own, regardless of trailers and updates.
People hyped it for eight years even when Nomura said flat out "We aren't making Kingdom Hearts 3 right now." Hype isn't going to stop now that Nomura is in press hermit-mode.
They have zero obligation to give us regular updates right now, and honestly I'd rather they concentrate on working on the game and show us the fruits of their labor when they have something worth showing because I have ridiculous expectations for what they need to reveal next. If they show a new trailer, I want it to have new voice acting, a handful of cutscenes, at least one Disney
(and/or Pixar) world, and finalized gameplay.
If they can't give that, then there is no point to releasing a new trailer.
Of course Nomura or Yasue should do a few interviews discussing more concrete information on the game, story expectations, and show off some key art or more cast and their new renders but if they can't because they are busy with other things, I don't think fans should expect anything. Like Shamdeo said, keep expectations low and you'll never be disappointed.