Since I like having this info there since people ... miss it.

Dio's appearing in Fam isn't a retcon of his 'dying' in the last episode because Dio never actually died in the last episode, despite what you ... see in the scene. Of course, it's not said in the series as much as it's said via other sources.

1) One hint is hearing Dio's voice later in the episode, saying 'ascending!'

2) The Aerial Log artbook confirms that after Dio fell, he was picked up by a Guild ship that had been passing by the area.

3) This post-canon official art.

So as you can see they handled this wonderfully.

Oh wait no they did not people still ask why the fuck Dio is alive in the sequel.