I imagine suspension comes down to intent to injure. Marchand is good (at both hockey and at douching) but I'd argue it's harder to pull off a no-look spear than a no-look pass. That'll be the argument for the defense. He definitely meant to give him a damn good whack, but the difference between fine and suspension will likely be if they determine he meant to give him a whack specifically in the nuts. If he smacks him in the legs there, it's likely a minor for slashing or roughing if the ref even notices. Because it's in the nuts, you can't be mad at at least a double minor, as it it your responsibility to be in control of your stick and he caused injury (though I'm not even sure if they call double-minors for spearing?) Major penalty is the right call, especially if the refs want to keep control of the game. Let the league sort it out beyond that.
If they do decide to suspend, I imagine it's for the rest of the regular season. If he only gets fined, I imagine a lot of people will be very upset because Marchand, but I'm sure intent will be the decisive factor either way. Honestly think it could go either way (fine or suspension) at this point, but some kind of discipline is definitely coming. Whichever they decide, I hope the DOPS clearly explains their decision.