It would be lame if we lost all the black suit's symbiote abilities at the end of the game and just get a regular black suit. From a gaming perspective, the symbiote would presumably give Peter additional abilities. It would be like if you as a player suddenly lost a bunch of web attacks at the end of the first Spider-Man game. Or if you lost a bunch of gadgets as Batman at the end of Arkham City.
This could work. I honestly have no idea how they'll do the symbiote as there's too many variables that weren't in the comics. Harry and Norman being involved already complicates the story for Peter (Will Eddie be involved? When can he wear the symbiote if Harry has it?) that I can't even begin to predict what plans they have for Miles.
I only liked Venom in TAS and The Spectacular Spider-Man, but I think the Venom in The Spectacular Spider-Man is the only one that works as an ongoing Spider-Man villain and maybe one of the "Big Three". The idea of the symbiote being a narcissist and Peter being in a toxic relationship with it feels more Spider-Man than the slasher genre villain McFarlane and TAS envisioned him as - that take was fine too but it's not as Spider-Man centric and doesn't work long-term because horror stories aren't the norm in Spider-Man comics (for example, the symbiote getting Peter to almost kill Shocker was effective in the way it was executed, but that seems like more of a Batman or Daredevil story than a Spider-Man one to me).
Granted I think the Venom/Eddie part in Spectacular was rushed. I didn't fully understand what they were going for with Eddie Brock until listening to Weisman talk about it on a podcast. But at least conceptually, I agree that Spectacular's Venom is the best.
All the more reason why I don't think Miles will be a main playable character in the next game. I suspect they'll let us alternate between Symbiote Pete and Regular Pete like in Web of Shadows. "Alternate between Regular Spider-Man, Black Suit Spider-Man, and Miles Morales Spider-Man" sounds like a weird way to market it, it would be like if Trevor and Michael in GTA5 were the same person (let's say a multiple personality disorder...I know this isn't a perfect analogy) and you can choose between one of the personalities or Franklin. That's why I think that, unless they also plan to give Miles a symbiote, he'll only get a DLC like Catwoman in Arkham City.The Ultimate Spider-Man game had you play as Venom and switch between him and Spider-Man at any time in the open-world. So maybe you can do that? You can also have Peter wear a cloth version of the black suit, which he wore after he got rid of the Symbiote in 616...and he wore the cloth black suit consistently until Todd MacFarlane came on and brought back the red and blue in a big way.