They can make good on the LEP in two ways, they can supply the product (their stated, if protracted intention) or offer to reimburse the customers not happy to accept the changed timescale. No hard feelings, the plan changed & it just didn't work out.
Instead the only info we have is a result of customers chasing up progress, and the majority of the bitterness is in the mind of other customers. I have spoken to FDev in person about this, they were extremely conciliatory and apologetic. They don't see it as a lottery ticket at all.
Since you got Horizons on your LEP, there is no way you can justify getting a refund. Unless of course you also hand back Horizons and take a cut on your refund for all the time that you were able to enjoy Horizons.
But you can't use the prices as they stand today as representative for the value you've received. Since you got both parts of the current Elite Dangerous sides (E and Horizons) at release, you would have paid the price they were going for at release. Which is 40 pounds for E + 30 pounds for Horizons, totalling 70 pounds. So if the next DLC costs more than 30 pounds, you've already saved money.Again, where did I say I'm entitled to anything extra? That's just your interpretation of my words and it's entirely incorrect.
At this point in time - I am worse off. I paid a 100 quid for something that currently costs 40. I don't know if the 2020 release will happen. I don't know what other expansions are planned after that. Considering the above and three fact it's been 5 years and Elite is what it is - I feel disappointed.
That's all.
And can we please stop saying that LEP owners get DLC for free. We get it at no additional cost, which is not the same as free.