He’s gonna end up looking like an uglier dk, I promise you 

It looks like it's back to Water for me. Nothing massively against the others, just Water has typically always been my pick. Gen 6 & 7 were exceptions (although regretted this in Gen 6).

I cant help but start guessing at the typings of the final forms. A lot of people seem to think Scorbunny will get an electric typing, but I'm not sure where that is coming from. That said, the only other one I can see if fighting, and we've had enough fire fighting starters. Grookey I'm also unsure on, but feeling maybe Grass fighting or Grass Dark. Being a lizard, Sobble make me think Grass Dragon. But others spotted his camouflage in the trailer and say that hints at water ghost, which has logic behind it.

ScorBunny, and I hope he evolves into a Fire/Dark type. That would be a good typing combination. Maybe he could evolve in a way that makes him look more and more like a disgruntled soccer player. Something like...

ScorBunny voles into....

ClosBunny evolves into...

RiotBunny

As long as its final form is not as atrocious as Diggersby

Maybe Sobble, but i'm waiting to see the evolutions.

Oh that would be sweet! And I can make an argument for that. Besides not having been done before for a starter, Scorbunny as an athlete is lightning fast, so fast he lights the ground on fire (that's due to his fire typing, but he doesn't have the electric typing until the final form so we'd only see the start of a theme at this point, like Sobble's camouflage maybe being the beginning of ghost type). You can maybe see the beginnings of Grookey being grass/rock, since he seems to be based off of rock and roll and is seen banging his stick against a rock for a drum. Personally I think either dark or ghost is more likely for Sobble than dragon since there's more logic to them than "he's a lizard" and also dragon is still a pretty powerful type, resistant to all three starter types and even electric.

But he's based on a drummer and Scorbunny is based on a football player, so what if Grookey evolves into a guitar player with wavy hair for whipping back and forth, while Scorbunny becomes a bulky goalie type? Jk, Scorbunny is obviously the speed/offense glass cannon, and I don't see Sobble being the hulking tank creature, though I suppose Game Freak could surprise us.

Funky long 

This is the first gen that i like all the starters, they are reallly cute!

Why grass/dark? He's a British drummer, not a death metal or emo band. Also, though it wouldn't make a ton of sense, they could make grass-ground, ice-water, and fire-electric, so that ice would be effective against ground and grass, ground against electric and fire, and fire against ice with electric against water, for near symmetry. Fighting-dark-ghost isn't perfect symmetry either, since ghost is entirely immune to fighting, not resistant. That said, if Sobble were water-ghost in the third form, I could see maybe Scorbunny being fire-normal? Don't know what you'd do with Grookey then, but you could just leave him straight grass. Some starter trios have done that before, with two starters having a second type but the third having just one.

Either way, I think Sobble has to connect back to UK culture or history somehow. With two of the trio already fitting that theme, it would be weird if there were just one that didn't.