Story wise : Going to Outland ?

Lore Story
1
Do you think that it's still possible to get to Outland, for the characters, after the destruction of the Dark Portal ?
2
There was a massive influx of Outland orcs during Cataclysm. That said, it was before the Iron Horde used the remnants of the Dark Portal to create their gateway.

But travelling from Outland to Azeroth mustn't be that complicated, there has been some recent movement regarding Illidari stuff and all.

Not as simple as it seems game-wise, but definitely possible.
3
The Kruul Mage tower has you going to Outlands so it is still possible as far the Legion 7.2. I think the Dark Portal is still active and still leads to Outlands, that would explain why you can't get to Alt' Draenor using ht Dark Portal as well.
4

It depends. To answer that we have to understand how portals work and if they are able to be created in a way to connect worlds and times. ( I mean normal portals like the ones in org… Not the dark portal or lore created portals ).
Personally I think that they will never answer that since portals are just a tool of convenience.

5

Afaik we still have a connection to Outland. We have to speak with a Naaru back in WotlK, Thrall was in Outland in Cata, we have the warlock green fire Questline (mop) in Outland. I need to recruit a teacher of rogues (a NE) during Legion in Outland.

6

Wasn’t there a whole thing about Outland slowly disintegrating into the Nether? As in, it will eventually be non-existant? Or was that just a theory?

7

It was mentioned during the Netherstorm quest lines