Wow... I got emotional reading this.

But is this just the end of act two! Oh boy... Well, preparing for war it is .

Just the end of act two? How much more is there? I would think this is just about to hit it's climax.

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Not many, but events get turned up to 11 from here on out.

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Hoooo, this is where the emotional pain really starts.

Wait a moment. Canon, plus fifty years, plus twenty five years. The Mane Six are in their nineties, and Celestia took them with her? What was she expecting them to do?

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They may be old, but the magic they carry isn't diminished with age.

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What magic? If they put the Elements back in the Tree of Harmony and the Rainbow Box of Contrived Solutions hasn't reappeared, they're down to their innate abilities. We've seen Wonderbolts in canon retire in middle age, so it seems reasonable to assume that they're unable to keep up with younger fliers. Similarly, Granny Smith is nothing like as physically capable as she was when she was younger. Fluttershy can presumably still talk to animals and I doubt that Pinkie Pie lost her reality warping, but they're still old ponies.

Ah, hang on. Did the Plunder Vines not happen in this story? Or did Rainbow Power stick around?

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The relationship of this series to the show has been pretty loose, as I see it taking place in an alternate universe that began after the changelings reformed (since that's when I stopped watching the show. In this new timeline, things have happened that did not occur in the cartoon, including the Mane Six somehow getting the elements back to carry within themselves, thus having powerful magic once more.

You know...given how several times in this story, and several times in the previous stories, Silverspeak is able to convince himself to be the better stallion or to keep fighting on 'because that's what Celestia would do'...I can't help but wonder if we're going to get some ironic failing on Celestia's part once Silverspeak finally meets her. Maybe she'll do something that will be morally weak and shatter Silverspeak's opinion of her. Or even more, maybe she'll sacrifice thousands or tens of thousands of ponies to save Luna's life...so Silverspeak revealing the resistance base will have been exactly what Celestia would do. That may even be what 'Sunfall' refers to.

Well, that's just me tossing a hypothetical out there. It's probably not what will happen, but that would have been neat. And that assumes Silverspeak ever actually gets to meet Celestia.

Still, as far as pacing and story narrative goes, it doesn't feel like this is yet the 'final encounter'. The penultimate encounter, and they'll probably rescue some ponies, but I think there'll be one more scrap after this. Maybe a Big Bad behind the Big Bad, to use TVtropes jargon.

One thing's for certain. Once this war is over, and ponies begin to rebuild, no unicorn is ever going to be able to lord his or her horn over the other pony tribes. All an Earth pony or pegasus needs to do is say 'Mangus Bluehorn' to shut up a unicorn. Considering how much of the death and destruction in the entire series Mangus is responsible for, it'll be rather a little like the Germans and the Nazi party.