To re-rail this thread, I'm putting this out here:
"Long post - and it's all about lore stuff and the relay network, so if your problem is the LI stuff, I feel your pain, but this isn't the topic for that.
I wanted to clear up a few misconceptions I've seen around here and on BSN. First, a disclaimer: I haven't played ME3 yet, and I'm going off of what the leaks are saying about the endings, particularly the destroy ending, but I guess the others too, though I'm not as clear on what exactly happens in those.
OK... there seem to be a lot of people with a reaction of "The galaxy is doomed forever!" Or, at least, for thousands upon thousands of years, based on the destruction of the relay network. But, lore-wise, there's no reason to believe that's the case.
First, let's establish what exactly happens in the ending, according to the leaks. Synthetic life is eradicated. The relays, in the process, essentially "overload" (seems like the best analogy I can come up with - they don't go supernova like the one in Arrival did). Contrary to what some chicken little types are saying, element zero isn't eliminated/neutralized. Mass effect technology, including conventional FTL, is not affected. We are not reduced to bows and frickin' arrows.
Second, let's explain the epilogue in terms of the larger technological picture. Now, there's an interesting theory that it's not the descendants of the crew of the Normandy, but rather the result of some time-capsule VIs telling Shepard's story that Liara apparently said she was going to distribute all over the place. Interesting, but for the sake of this argument, lets say it is the descendants of the Normandy crew. With the relays being destroyed and them ending up god-knows-where without any method of interstellar travel or FTL communications, even if everything got back to being hunky-dory in the next couple of years around the galaxy, it would still be like looking for a needle in a haystack. The galaxy is HUGE.
As for the rest of the galaxy, I don't think it would take that long to rebuild. At least they have blowed-up relays to study now - decent enough chance they could figure out how to build new ones. We know that he Protheans were pretty close to figuring out mass relay technology when the Reapers attacked, and managed to build a small-scale one eventually - the Conduit. Additionally, the FTL comm buoys, which were built by the citadel races, are stated in the codex to essentially be primitive mass relays. So, we have the concept pretty well in hand. If you remember, Matriarch Aethyta at one point pushed for more relays to be built. It's almost certainly feasible in even a relatively short period of time - the reason it wasn't worked on more before is probably simple economics, since they already had a pretty comprehensive network.
Also, some people are vastly underselling the effectiveness of conventional FTL in this universe. According to the wiki at least, it's about 12 light years a day. That would mean getting to Noveria (in the Horse Head Nebula) in about 4 months. Illium (in the Crescent Nebula) in about 14 months. It's a bit of a haul, sure, but it's feasible, at least to be able to share information and scientific progress. The biggest problem you'd run into isn't so much getting there in general, it's finding enough good places to discharge your drive core along the way, since a lot of the route probably isn't mapped.
With a major multi-species focus on the field, it wouldn't be too surprising to see at least small-scale relays like the Conduit, capable of transmitting communications and maybe people and supplies in relatively limited amounts, within a few short years."
Source:
http://www.gamefaqs....fect-3/62134320