I'm thinking what we're looking at isn't a sword but a sort of pistol. Fairly convinced it is. The holster is too short and while Predator weapons are collapsible and don't have to conform to what they're actually stored in (been a thing with Wristblades for forever), I'm fairly certain that's a pistol.
I don't think it's a speargun though. The spear in the trailer I'm also fairly certain is the spear on his belt. We've seen them throw spears before in both the solo and crossover films as well as games. So I think it's more likely that's what he's hit by. It also doesn't look like it's on his belt in the same place when he's leaping through the trees.
Honestly it's probably a dedicated plasma pistol. Tractchenberg is probably playing coy. There is no shoulder cannon, but Feral absolutely still has a plasmacaster, it's just in pistol form. That's not out of the question, Hunting Grounds has a dedicated pistol and while Wolf's doesn't resemble it, Wolf's wasn't a pistol to begin with. It was an improvised weapon.
As an aside I don't like the smaller dreads. Practically I think that makes sense for a smaller head for Dane's suit. But I think the texturing was the better update for them. I'm torn on it given I can see the usage but I don't think it looks as good. Also in the still you can see the seam in the suit. Not like they're going to focus on it but for the screenshot or really any post-production you'd have hoped they'd cover that. Not a deal breaker but had they lowered the backpack to his actual back rather than sling it over his shoulder we wouldn't be seeing it as easy. Not a deal breaker like I said, it's not that noticeable and if I can accept the various goofs with stormtroopers I should here.