Elsewhere, someone pointed out we'd actually seen the new enemy before on the conspiracy wall but from a side view angle:
So though I thought it was the Hunter Gamma as I posted before, but after some though I've concluded I think it is the Grave Digger, or at least a worm enemy.
The reason why is I remembered Tremors 2 existed.
So Grave Digger from RE3 was always a big reference to Tremors:
Now the thing is, in Tremors 2 the Graboids (the name of the monster worms in the Tremors series) evolves into these things:
I actually think Capcom's decision here is just to make the enemy a big Tremors 2 reference (which Grave Digger was always a big Tremors reference, so that's fine I suppose). I do wonder if we'll still get a giant worm as the main one or if they're like the G-Adults in RE2 and been turned more into a regular enemy, but I'm actually highly amused they may have just decided to make the enemies a big love letter to the Tremors films.