User blog comment:Arbington/ME3 Theories/@comment-1903421-20100628203532

Interestingly, if you reveal the evidence about Rael'Zorah, Tali talks afterward about the Migrant Fleet being on the verge of disbanding, with some ships going out on their own to look for colony worlds and others preparing for war. That's one case where the decision you make in ME2 is going to make a huge difference.

Here are what I see as possible outcomes from the quarian-geth conflict:
 * If you asked the quarians not to go to war, they will survive and establish a ceasefire with the geth.
 * If you encouraged them to go to war, they'll try to retake the homeworld. Daro'Xen will complete Rael'Zorah's research, to devastating effect against the geth, and the quarians will retake their homeworld; but both sides will be decimated and of no help against a Reaper invasion.
 * If you didn't take a stance one way or the other, or if you presented the evidence of Rael'Zorah's guilt, then the Migrant Fleet will disband. The ships that move against the geth will be wiped out, while those that seek out new colony worlds will begin the generations-long process of adjustment. The geth will still be in decent shape to fight the Reapers, but the quarians won't.

As to the Reapers themselves, they're going to suffer from attrition trying to get back to the Milky Way the long way. Mass effect drives are Reaper technology, and mass effect drives have to discharge their electrical fields at some point ... and not even Reapers get to break the rules. They'll have to use other Reapers to discharge, as there's nothing else in dark space they can use. This will "cook off" as much as a third of the Reaper armada, and it explains why they didn't just start heading in after Sovereign's destruction.

As to the heretics, military capability may be the only difference. The heretics are small in number (5 percent) compared to the main geth population, though they may have more hardware platforms for a fight against the Reapers. I'm going to go out on a limb and speculate that this decision won't be a big deal one way or another.

We'll see all the surviving crew members from ME and ME2, though they won't all be part of the crew for ME3. I expect Tali and Garrus will return, but I'm not so sure about any of the other ME2 squadmates. We will almost certainly see Shep's ME and/or ME2 love interest(s); Bioware's all but said as much. Beyond that, we'll get a couple of FNGs to round out the ME3 squad.

The Collector Base: It'll be interesting to see what comes of this -- it's the climactic decision from ME2, yet it may or may not make all that big a difference in ME3. I suspect the humans will have an edge on the Reapers in the electronic warfare department by virtue of the Reaper technology incorporated into EDI. Saving the Collector base may reveal other Reaper weaknesses, but I suspect these will come to light even if the Collector base is destroyed.

Miscellany: The datapad at the end of ME2 is the concrete evidence Shep needs to prove the Reapers' existence. But what will the Citadel Council make of it? I'm going to throw out a wild hypothesis that the Council was subtly indoctrinated between ME and ME2, and that Shepard will have to either maneuver around them politically or stage a coup to unseat them in order to get the Council races to mobilize for the invasion.

My 2¢ (for now) ... :)