The above could be construed as a breach of Consumer Law in the relevant jurisdiction (UK). Therefore there is a potential cause of action that may argue for restitution (refunds).
To put the internet not-actually-a-lawyer argument for the defence:
Summary: Frontier's actions are upsetting, disappointing, worrying, angering, and a whole bunch of other stuff too. They're not illegal.
1) The console players bought Horizons, which was sold as Horizons. They were delivered Horizons. Frontier will argue that the dreams of playing Odyssey later have no tangible value, as many people have bought Horizons for the same price with no intent of playing Odyssey, that Horizons has value in and of itself to the amount charged, etc. etc.
2) Anyone wanting to play Odyssey
but not Horizons on console has no reason not to wait until Odyssey was delivered to buy that. Frontier will then drag out your play time records in Horizons as evidence that you at least weren't
solely motivated by Odyssey availability, but also wished to have access to Horizons, which you still do. So any sort of refund is highly unlikely unless you bought Horizons but didn't actually play it at all - in which case, just go get the refund from your sales platform. (Buying any ARX for Horizons content
damages your case here because it shows you enjoy and get value out of Horizons in itself!)
3) The maximum you could even implausibly claim as damages would be the amount you paid for Horizons. No actual lawyer is going to get out of bed for that little, so you need to represent yourself. Remember that there is a chance - if you mess up your case dramatically - that the judge may award costs against you, and then you'll have to pay for Frontier's lawyers too (highly unlikely in normal court operation, but in normal court operation you'd be represented by a competent lawyer who'd not bring the case that far if that was a likely outcome).
4) There is absolutely no chance that UK law - we're a business-friendly jurisdiction, in the sense that we allow businesses to operate! - can be construed such that on the shutdown of an ongoing service, people who had previously paid for and used that service while active without complaint get refunds for that too. There's no "Bob's MMO has closed after three years, all purchases get refunded" precedent or law for very obvious reason. So if actually removing the service entirely wouldn't be in general grounds for a refund, deciding not to provide a not-yet-paid-for enhancement for it won't either.
5) Even in the event that your case succeeded, Frontier could declare that it had restarted console development, and therefore was delivering your dreams of being able to play Odyssey in future again. This could be one developer, one hour a week, expected delivery date 2175 - because they stated back in July that they were switching from "expected date" to "indefinite delay" on the console release, and you didn't raise a claim then (See point 2, you'd better not have
played since then!) - so you've already shown,
especially if your purchase was after 12 July, you're not paying for an actual target date, just the dream that it's possible in future.