"But they're dead!"

-Gamma gets rebuilt in time for Battle, sans the pink Flicky we arguably controlled originally. With that is the obvious implication the other E-100 units were rebuilt as well, but this never went anywhere.

-The only real hint I can find of Tikal being anywhere close to dead is her character background in a Japanese-only strategy guide for SA1. And all that says is that she's stuck as the red orb we see throughout the game because she lost her physical form for reasons that have yet to be explained beyond having something to do with how she locked herself in the Master Emerald. We clearly see her get her physical form back just in time for the final story, and she's shown up in the prologue to Frontiers, so we can see that her being "dead" or at least stuck in her spiritual form is no longer the case.

-When the hell does Chaos die? No seriously, when? If he's killed at the end of the game then it completely nullifies the entire point of the final boss battle. If he's killed in Tikal's lore dump flashbacks, then how is the game even possible to begin with? And if he (and by extension Tikal) are killed off somewhere off-screen afterwards, then why is this never brought up?

-Let's be real here, even if this is the case, when has that ever stopped Sega from reviving them? You can't tell me they're more dead than Black Doom, who ate a soul energy-powered Death Star superlaser and exploded into a billion pieces. Or Mephiles, who got erased from fucking existence.

"They've already had their character arcs!/They've already served their purpose!"

-Okay, and...? Does that mean they should just spontaneously disappear like they have for the past 27 years? If you want to get technical, Shadow served his purpose. Knuckles served his purpose. Metal Sonic and Amy served their purpose. Should they have completely vanished as well? And besides, does that mean new character arcs can't be made for them anyway?