I really don't see that happening.
Fitz came forward "the long way". They've already jerked around Fitzsimmons enough that I don't see them doing so again; the current issue is bullshit enough without pulling a "Fitz gets left in the future/dies when the rest of the team, including Simmons, gets to go back".
What I imagine will happen is that they'll go back via the stone, to a time point just after Fitz froze himself, so there's only one active "Fitz". Which opens up descendancy again.
Though I imagine they're also going to figure out how to prevent that future. Given the reveal of gravitonium in the last episode (I'm only using spoiler tags for the most recent episode stuff, since if you aren't following the show, why are you here?), I expect the finale to be something like;
Quake isn't the only reason the planet blew up. Graviton is the main reason. And he's active somewhere on the remaining shard. Maybe nuts, maybe antiheroic, but regardless, it was fighting Graviton that caused the planet to go "blooie", not Quake. So the end point of the season will be going back to the "real present", finding Graviton before he powers up, and making sure that future never happens. And that this is why they're here; not to help the humans of that time, but to make it so that time never comes about.
But that's admittedly based on that otherwise-out-of-place reveal last episode, and that if you follow the comics you recognized some stuff from a few seasons back and knew this could be coming.
Deke is supposed to be giving off a major Peter Quill vibe to the audience right?
I mean, technically. But we know what they oral history says, and what the Kree think. Thanos, in particular, isn't particularly stealthy.
Meanwhile, there's little reason to make a point of mentioning the gravitonium last episode unless they're planning something. Otherwise, it's a weird callback to Season 1 for no real reason to answer a question nobody was asking in the first place. So I'm assuming it's a Chekov's Gun; that reveal means something important. And there's really only one thing that springs to mind, as I detailed above.
I hate timetraveling. There are already inconsistencies. Daisy apparently quaked the earth apart. But since she is now in the future, how can present earth be destroyed.
That's not an inconsistency, unless you're operating with a fixed timeline. Which arguably they aren't, visibly, by the fact that this is happening. And even then, if they go BACK, and the Earth gets destroyed (either by Quake, because it's the right thing to do and we don't know it, or by someone else and Quake gets the blame unfairly), then it could still BE a fixed timeline. Until the history you're living in the present diverts from the history you know of from the future (and that history was correct in the first place), you can't disprove a fixed timeline.
If it's a dynamic timeline (like the Back to the Future films), then they've popped forward to the future that existed when they left, but going back and changing their actions can prevent that future ever occurring.
And in a multiverse view, they popped into a future, and will pop back, and follow a different path forward to a different future. Which doesn't mean the first future is gone, it's just a different branch.
This gets weirder with Marvel because the various multiverses are somewhat but not completely related to timeline differences. Some multiverses involve important changes in the timeline, others are just wildly different. But the point is that there's nothing inconsistent at this point, even if we assume a fixed timeline, which we shouldn't.
Who the hell is Finn....
The way I saw how time works.
Time where Daisy goes to fight someone and causes the Earth to break apart. This causes the deaths of Mac and Coulson as well. Jemma, Fitz, May, Yo-Yo and Robin all get out on the Zephyr. They get to the Lighthouse to survive the intending apocalypse. During the plane scene May says that cities are starting to black out all over the world. So they originally end up living out a life where May is Robin's mom and Fitzsimmons try and build a time machine. Robin having the gift of Foresight and having essentially lived that entire life tells her present mom and Enoch about it. They put into motion the events of where they currently are.
The only part I can't reconcile is Fitz says Voss tried to fix it and it didn't work. Which has me believe the part we see where they are trying to blend in with everyone at the Lighthouse. Is them in the future after they've tried to change the timeline. Since Voss tries to preemptively kill Daisy to prevent her. Or perhaps Voss succeeded and the world was still destroyed.
This whole episode actually wracked my brain when I watched it last night. Kept thinking on how it would work.
And now to wait 4 weeks until the next episode. Bloody Olympics.