While I agree that there will probably be visual improvements from Episode Duscae to the actual retail release, I don't think the Luminous Engine version numbers can be used as the basis for any argument. They are arbitrary and without changelogs really tell us nothing other than that they are still developing the engine, not necessarily improving graphics.
Sure, some revisions may have more improvements than others.
The difference here is that they've clearly stuck to their word and upgraded the game, and also said that more upgrades are to come. There's no reason to not believe when this is the one aspect that they've clearly delivered on thus far.