The matter of the throne in Zephyr Heights - which may have been a place of residence for Twilight at the end of her reign just before the collapse - makes it clear, along with the episode in Bridlewood, that only an alicorn could bury these parts of the blanket. The throne may indicate that the alicorn magic was not gone in contrast to the rest of the magic during all the time the ponies were without magic.
From the movie we have learned that Equestria’s collapse had not happened “that long ago”, the state of the airship station dispelled all theories about a long time between the G4 ponies and the beginning of G5. Everything points to 100 to 200 years.
From the IDW comics we have learned from Izzy that more than a century had passed since Canterlot was abandoned, again we arrive at between 100 and 200 years.
The MYM special had revealed that the dragons were last seen several generations ago, suggesting that the ponies remembered them from the aftermath of Equestria’s collapse. Here up to 200 years, as a generation is usually between 20 and 40 years. For the humans 30 years, the ponies may have less or longer generation time, we just don’t know.
In the TYT it has emerged that a prophecy was predicted “ten generations ago”, between 200 and 400 years. But there are many indications that this happened well in advance of Equestria’s collapse, not least because the lighthouse had a mechanism meant for the Unity Crystals.
Then it boils down to the time of Equestria’s collapse being roughly 150 to 200 years before Sunny’s birth. Most likely 200 years.
As Queen Haven said “centuries” based on her knowledge of the history of the interior of her palace and Zephyr Heights seemed to have been massively developed in less than a couple of centuries, that could mean that Twilight sat on the throne as little as a couple of centuries before the start of the G5. The old throne looked like it was meant for an alicorn.
That means there were four generations between Equestria’s collapse and the return of magic.
And since we know that Discord can use smartphones at the same time that TYT has revealed that the technological gap between pony tribes is not as big as thought, it must mean that the G5 world has arisen during Twilight’s reign, maybe she was the one who invented the first the smartphone. This could mean that Twilight could have become a G5 pony, we had received indications of this from the work on the movie.
Twilight knew about Sunny. She knows a new alicorn will arise. But the details on the blanket suggest that she simply did not see the indications about Sunny and her friends, as the old lighthouse from the posters is shown. She possibly knows that it can happen after her disappearance, although it is obvious that the blanket was made with a purpose that is still not revealed. She knows what family lineage Sunny will be born into. That might explain how Argyle got the feather from her, it might have been a family heirloom.
So when Twilight experienced the darkest moment when Equestria came under attack by The Big Bad who was so strong that Discord was traumatized and that no magic could stand against the attacker, at least she knew there was hope when she broke open the Unity Crystals and shut off the magic from the world.
So we can only hope that The Big Bad doesn’t know about this…
