Based on any Pokémon games from X/Y onwards, you have never been able to transfer over freely just like that. With X and Y you had to wait for an application to release that enabled you to transfer over from Black and White. With Sun and Moon you had to wait for a Pokémon Bank update that took several months to release.

On top of that, the ability to send over Pokémon from earlier games has usually been a "post game" reward. Meaning that only after defeating the Elite 4 and Champ you have traditionally been able to receive Pokémon not available in that game. IIRC in Black and White not only did you have to go through the league, you also had to fight your way to the end of the opened Post Game regions to unlock that ability. It has never just been handed out to you.

Besides that the creators already SPECIFICALLY mentioned that they want to prevent another generation 2 to 3 disaster of being unable to transfer any over.

All the info we have right now is a single line said by some person at the Treehouse that may or may not have been somewhat mistranslated. And they also mentioned something along the lines of "for the adventure…" which could refer to the game before being crowned champion.

So yeah, I think an update will take care of that and that it won't be a permanent thing. In all likelihood because not all data required to make an appearance (like walking animations).

Why do I get the feeling this is some stupid misunderstanding that people are blowing out of proportion?