Season Five Hypothesis · 4:27pm May 31st, 2014
The rest of the Mane Six will become alicorns.
Reasoning: The show writers have stated that Twilight won't outlive her friends. Nor that her lifespan was the same as before. They also haven't stated her friends could not become immortal like she possibly is.
To me, that sounds like they were hinting at something. Something BIG. Something both Wondrous, and at the same time Divisive.
Side hypothesis: Shining Armor becomes immortal. (reason: Cadance's marriage otherwise sounds doomed from the start. And I don't think she'd pull the Together in Death card)
To those who read this: thank you for reading my ramblings.