There is still no plausible reason for Foehn NOT TO use a Time-Machine AFTER they defeat Epsilon
Foehn's technology prevents global warming, vastly increases lifespans, provides much better living standards, etc.
They can design the Time-Machine to be only USED ONCE then make a pact to NEVER use Time-Travel again!
There would be just a few hundred million (out of several Billions) people left after Foehn destroys Epsilon. There is no future after that
Realism wise, few milions would be more than enough to restore humanity, there were fewer Humans in history than that, looking around the internet throws some numbers at me, but it seems 500 Humans are enough to prevent extinction AND to evade inbreeding problems.
So yes, if only Foehn Revolt were to remain, they could still repopulate Earth multiple times over. There would be also a hidden bonus playing to Foehn's cards and that because its composed from survivors from militiaries and the best of the best, this would serve as a seal of quality of its personal that they are likely to be the best of the best in terms of mental and physical health so nobody can taint the DNA integrity of the new humanity with crippling genetical defects. Such crisis will also remove everyone too reliant on health care...quite the cruel natural selection, but Humanity will carry on.
And no, you can fight me on this but i rather live in a world that still resembles our own, just being desolate and war torn, this wouldnt be anything new to humanity. The solace of low population would also mean there wouldn be any petty wars (maybe ?) and resources would be plentiful so no wars due to oil or uranium would happen for really long time.
Living post third tiberium war, once GDI get the TCN towers up...yeah, in that moment it would be better than in Mental Omega universe.... if we ignore the fact that the Scrin are out for revenge and want to eradicate humanity, this time with actual military.
And to remind you, Scrin can create blackholes and wormholes, and the miners were armed with such things. So living in Tiberium universe would carry some...existential dread.