Seems he's evolved his position. I kind of like the trailer, I didn't expect to. I think the flow with the boxes being dropped worked out well. Maybe he'll do it well.
That's interesting, I guess you could interpret it that way now that I look again. But to me it looks like cell shading. Taking a peek at Tales of Monkey Island and MI4, this one looks like a great improvement. Probably why it impressed me.
If it is 3D, the camera angle doesn't change much but at least the ship seems to move just a little or something. And the boxes that the guy drops seem 3D. But maybe it's just artistry, who knows.
It's also interesting to look at the other products from Devolver Digital, for instance Weird West [1]. It has 2D look in 3D world.
Since Return to Monkey Island will be point and click, I too suspect that camera angle won't change much. I think interacting with the scenes is basically 2D.
With 3D scenes the user would be forced to turn the camera, and I think that is too much for point and click.
Weird West's shading is great, but it's still clear that it's a 3D world even from still screenshots, while Return to Monkey Island looks clearly 2D even when animated. Everything in RtMI trailer is flat, ship's parallax is a simple transformation, Murray and seagul are obviously flat and keyframe animated the way 2D animation is done, you can see handpainting on Mêlée Island and the water around it. Plus, of course, this is the kind of game where they would gain pretty much nothing from trying to make it 2.5D (and making it convincingly pass as 2D-looking is a lot of work). I'm absolutely surprised that anyone thinks it's 3D, and in fact this is the only place I've seen anyone suggesting that at all (everywhere else people are discussing the art style instead, which seems to somewhat borrow from Special Editions while making it distinctly modern and a bit more cartooney).
BTW. If you're into cell shaded stuff, check out some of the Telltale's stuff like 2012 The Wolf Among Us (which has a sequel being worked on now).
I'd rather say that you probably haven't seen a lot of modern, quality 2D animation out there. I'm 100% sure it's 2D, and other hints (like the fact that Delores seems to be an engine demo for Return of Monkey Island as the timeline matches perfectly) also point to it not being 3D.
https://grumpygamer.com/if_i_made_another_monkeyisland [2013]