After every reset in Edge of Tomorrow, Cage "wakes up" at Heathrow and everything is as it is (all the dead are alive like before). In the end Cage destroys the Omega's core, and its floating blood once again give him the power to reset time. He "wakes up" a day before en route to his first meeting (and why not at Heathrow like everytime?). But how come the Omega is not alive again? In other words, why are the events at the Louvre Pyramid not reset?
Why is the Omega not Alive after the restart loop?
The Omega (Core) is the "Time Machine" that allows for Time Travel!
How could a dead Omega restart the time loop again? IT CANNOT.
If the Alpha is killed, the Omega simply restarts the day. If the Omega is killed, well... That's it. Restarting of the day cannot be done because the thing that actually did it was destroyed.
Why did Cage not wake up at Heathrow like previous occasions?
We must establish a timeline:
Day of Beach Assault is *D-Day* Day prior to Beach Assault is *D-1* (D minus 1) Day after Beach Assault is *D+1* (D plus 1)
Cage's wakes up at Heathrow on D-1. He spends the night in the base. On D-Day, he kills the Alpha and is covered in the Blood that gives him control of the restart loop that takes him back to D-1.
He receives the power on D-Day.
On Cage's "winning run", he actually went to go see the general on D-1. He lost his power on D-1. Furthermore, the attack on The Louvre also took place on the night of D-1.
He receives the power on D-1.
Since William Cage acquires the ability and activates it sooner than in his original first time, the restart loop must then aslo start at an earlier time as well.
If you noticed the repeated events on the beach head, loop after loop, we never see the Alpha again. The Alpha cage killed stays dead on the following loops. Later on, when Cage is lured into a trap by the false vision, another Alpha is there, and they attempt to keep Cage alive, or atleast drain his blood. We are told that Cage absorbed the first Alphas power, and then told that Cage is the Alpha.
Cage killed and became the Alpha. That dead Alpha was removed from time/future loops.
That means the only explanation for the Omega not surviving the reset is that, like the Alpha Cage had killed, Cage has become and replaced the Omega in the time loops.
Cage is the one who resets the day after he kills the Omega.
There are many Mimics, only a few Alphas and only one Omega.
The first time Cage gets some of the alien power is when he is covered in an Alpha's blood, not the Omega's blood. Cage aquires the power to reset the day, not the Omega. The Omega starts searching for Cage as it wants to find him to bleed him to take away his ability to reset the time loop and then kill him. As Dr. Carter says, it may be this ability of humans to get this power that is the creature's only weakness and humanity's only strength. It is Cage that resets the day back to Heathrow.
In the end when Cage kills the Omega he gets covered in the pure blood of the Omega, not Alpha blood, and Cage acquires the power of the Omega, which logically should be much stronger than the Alpha's. The Omega dies first, and its blood covers Cage and as a consequence again gives Cage the power to reset time. The Omega can not come back to life because once dead, it stays dead - it is humanity's ability, not the alien's, that allows the power transferrence to Cage. Cage is now in control and he resets the time to when he is in the helicopter flying to London, with all those he's learned to care about still alive.
This to me is the most interesting part of the plot, and why I love this movie so much, - that we are left to consider what other powers Cage has acquired, and how he might use them throughout the course of his life. Perhaps he never dies, but turns time back over the years to live countless experiences. And if another Omega reaches Earth, could he use his powers against it? Since it's Omega blood and not Alpha blood, is it possible that he may never lose the power? The possibilities are endless, and I never get tired of watching this movie.
I think Cage has replaced the Omega and now has the power himself to reset time although perhaps he can't activate it without something similar to an Alpha. I'm uncertain in the end which of the two (i.e. Cage or Omega) resets the loop, but it could be either or both at the same time. Perhaps this conundrum is what causes the reset to happen earlier in the day with the Omega remaining dead and Cage alive. The reset happens right after Cage gets covered in the Omega's blood and the Alpha that was chasing him is already toast. So I think Cage both activates and resets to an earlier point in the day and because of whatever strange juicy time weirdness the Omega actually is... it remains dead as does the reset of it's organism. Cage receives this new power on d-day as they left to Paris an hour or so before the launch of the allied invasion, which is about right for the extra hour or so on the last reset.
As far as why the Alpha was not seen again on the beach, well the Omega knew it died there and it remembers everything as well but simply does not have the ability to activate the time reset. As Dr. Carter states "the Alpha is it's central nervous system" which sends/activates the response to reset time. So the Omega would not send the Alpha in to die again and again but instead holds it back to lay a trap for Cage. Perhaps the Alpha at the dam is the very same one from the beach as the omega would have had almost a full day to get it there.
It will be interesting to see how they script the sequel. Perhaps there's another alien Mimic asteroid in orbit that monitors the invasion and will come down or perhaps there already is an Omega seed that was already planted and growing somewhere in Europe. Will it be a battle of Omega cage vs. new Omega baby? Multiple time resets happening from two separate time controllers? It should be a wild ride if done as well as this movie.
I assumed that it WAS the Omega that triggered the final reset in the movie as an act of desperation. I further surmised that (a) this was the first time in the history of that species that it had ever encountered a species such as humanity, that could 'hijack' it's time-reset-ability, and that (b) due to the Omega's decided lack of familiarity with any kind of experience in having its time-reset-ability hijacked, the Omega just assumed that if it reset the day after Jack Reacher... I mean Private Major Cage KAbOOmeD it into the next dimension, well, I expect that the Omega assumed that time would be reset and the Omega would return to life. However, as their race had never encountered any such thing as humans, it had no way of knowing what would actually happen. So, as I surmised/ guessed originally, I suspect that it was indeed the Omega who triggered one final time-reset, but that in doing so, the Omega itself was not affected/ not reset/ not regenerated, because of something to do with Cage being in control of the power now?