Horizons If i bought beyond (when it comes out), would i also get the horizons content?
Beyond IS Horizons content.
So, if i buy the season pass whenever (even in 2018) then it includes everything?
That's how I understood it. It's gonna be an overall improvement of gameplay. Be it Vanilla or Horizon.
Yes, as it was stated, all content announced at FX will be available for free to Horizons owners.
There will apparently be additional paid content coming over the course of 2018, but there have been any further details about that.
... except the base game - Elite Dangerous - which is obviously required to be expanded by Horizons.
If you buy Horizons now, effectively you are getting another year of free updated content, called Beyond.