Show me where they promised you on your games packaging or EULA that you will get to finish the entire DAI story, DLC and all, on your last gen platform. You are owed nothing.
As someone who own Dragon Age Inquisition on Xbox One: I disagree and -I mean this in a way that is respectful of your opinion- find it to be a ridiculous argument. If the tables were turned and only last gen got the DLC and current gen did not, but the packaging or the EULA didn't state that we got the DLC, would that be reasonable? Of course not. It was reasonable for anyone who purchased the last gen versions -as with the current gen versions- to expect to receive all of the DLC, especially after they got the first one.
If anything, they should have announced pre-release that last gen consoles would not receive all the DLC (of course they didn't because that would hurt their sales). I'm positive that more than a few people who bought the game on last gen consoles would have waited to purchase the game until they had a current gen console had they known that all of the DLC wouldn't have been available to them.
I'd say that they are owed the exact same as those that have it on current gen consoles because they bought the exact same product and for the same price. If anyone says no to this then I ask, what makes us better than them? We aren't better or more in the right, we all bought the exact same product. The only difference is the generation of console that we have it for.