By the will of Randominous, I hope you are wrong... but I suspect you are right.
Certain ships are locked to horizons only, such as Beluga, Dolphin, the Alliance C series, Type 10, although strangely not the two Kraits. The reason for that is the addition of the new ships were part of the chapters of horizons. Although the Kraits came as part of beyond which I thought was meant to be for horizons players? Whatevz - I don't want to snider anyone out of any ship, including the Cobra Mk.IV I have access to.It's not planetary bases, its horizons, even in base game at Jameson Memorial you just cannot buy them, something I discovered by accident when once upon a time my SRV got stuck, switch to non horizons, docked at shin dez and couldn't buy a chieftan. Aye ok.
I've been thinking about this, odyssey only server rumour thats sprung up in the last 24hrs, and I think I can see some logic in it. Specifically - the planet from the Odessy trailer looks nothing like what we have in galaxy at the minute, very small and has a (presumably thin) atmosphere. Most planets that size do not have atmospheres, so it is plausible a new seed, or other tweaks/work to the stellar forge will be required for it to create such planets. As such there would be a different galaxy for Odessy with its new tweaked stellar forge that creates the new planets with atmospheres that its players can land on, and the OG* that we have now. So future updates bringing in new stuff would need to be adapted to the old galaxy, duplicating upkeep. If someone heavily involved with the stellar forge such as Dr.Ross could elaborate on the new planets and how they will be rendered in one of the future dev diaries / streams / newsletters etc - they could either confirm or allay that fear/suspicion.
Given what I know of how stellar forge works, well worth watching the discovery scanner stream with Dr. Ross, if we start making millions/billions of tonnes of gas adhere to certain rocky bodies this would have a shift in the balance of what matter was available for creating other bodies. So if you had a complex star system with a couple of planetary systems including 20 moons, 12 of which have an atmosphere, the 12 billion tonnes being used to create the atmosphere on the fortunate 12 might mean there was not enough material left to create the 20th moon. So it is not inconceivable that you could end up with a horizons system having an extra body that the odessy version does not, 400 billion star systems, and all those cascading changes?
Joining the dots doesn't draw a happy picture.