I really think that although it has been confirmed that Twilight will not outlive her friends, I think we also have to think about how this is a kids show.. It does not need to talk about if she will really live longer than her friends. If it was aimed for a higher audience, then maybe it would have been different. I think that yes, Twilight will outlive her friends, but will not be immortal. She and Cadence are both artificial alicorns. That being said, they still have their birth genes, but the artificial genes are sort of interfering. I think that Twilight will age much slower. Celestia and Luna were confirmed by Lauren Faust that they were, in fact, born alicorns. They most likely will live forever. Even though Twilight will probably live way longer than her friends, she probably WILL pass on.
Now another thing to think about is that maybe she might just actually live forever. Why would Princess Celestia turn Twilight into an alicorn if she probably knows she will die eventually? Is she just planning to make a new Princess of Friendship as time goes on? Well, maybe, actually that's probably where Starlight comes in... But really... Not everypony has potential in being a princess. It has to be earned. We know what happened with Sunset Shimmer. What if there was a moment where it happened again? The student betraying the teacher? We just have to keep the fact open that Twilight may actually live forever.
Wow, wish I could do this good on essays XD
Tell me what you think about what I said.