@chealec:
What's a few billion years to an immortal God like Shepard? Or beings like Reapers and Leviathan? Lol
For that matter. What are 4 billion years? You are speaking and thinking about this entirely from the aspect of a terrestrial Earth perspective. And within the constraints of time and life as defined by Earth years/months/weeks/days/minutes/seconds and etc. A galaxy that travels and organizes itself around faster than light physics, Mass Relays, Life in dark space, would exist around completely different references for space, time continuums. What would 4 billion years evn mean for an Asarian or Geth? Your response suggests that you are thinking about the looming Milky Way & Andromeda dustup purely from an Earthly human perspective, circa 1950-2015 timeframe. Certainly not from a Mass Effect viewpoint.
I'm not talking from an Earth perspective, that would be silly, the Earth is only 4.5 billion years old. The age of the entire universe is estimated to be less than 14 billion years... you're lacking a sense of perspective here I feel. 4 billion years is a really, really, really, really long time - 29% of the entire age of all the matter and energy itself released from the Big Bang.
What would 4 Billion years mean for an Asari? Well let's see - 50,000 years ago they were basically blue Greeks being uplifted by the Protheans so their culture was a little more advanced than that of humanity (they had maybe 45000 years on us)... multiply that level of regression (50,000 years) by 80,000 times. Given the fact that Thessia is only slightly further out than Earth from the galactic core it's reasonable to assume it's no more than perhaps a billion years older than Earth, so 4 billion years ago it would just be cooling down - the very first seas might just be beginning to form; the Asari would probably still be a good 3.999 Billion years away from even evolving into something recognisable as Asari.
Even with Mass Effect's slightly dodgy grasp on timescale, the first Reapers only came into being about 1 billion years ago.
Oh, and the game hints at Dark Energy destroying the star of Haestrom faster than expected - which sort of ties into the Big Rip theory in which Dark Energy eventually overwhelms all other forms of energy and rips every single atom apart destroying the entire Universe in one gigantic singularity event... the estimated timeframe for this? Only a mere 22 billion years in the future.
What are a few billion years? Only potentially the entire life of the Universe from the very beginning to the very end in a mere 36 billion years total... does that help put it into perspective?
Retour en haut
And luckily asari will be leading us again because it was their idea to put plans in motion to ensure continuity of their race and culture. 
That would even the letting harvest us ending could be canon.(dat stargazer looks like prothean so maybe some protheans escaped andromera too and we are seeing them in the ending) Or they might just follow us to the andromera and destroy us again. 
