James Cameron confirmed that there are infinite timelines that create alternate realities. It works on the multiverse time-travel theory. What happens in one timeline doesn't affect the other. So the timeline of T3 and Salvation are unaffected by the events of Genisys and Dark Fate. The future of THOSE timelines are what changed, not the realities of the future they came from. This is different from, say, X-Men: Days of Future Past or Back To The Future, where changing the past altered the future.
These are the current known timelines/realities/universes:
T1 future (where Kyle comes from)
T1, T2, T3, Salvation
T3 future (where the T-800 comes from)
T1, T2, Sarah Connor Chronicles
Sarah Connor Chronicles future (where Cameron and Derek come from)
Genisys
Genisys future (where Kyle, Pops, and and the T-3000 come from)
T1, T2, Dark Fate
Dark Fate future (where Grace comes from)