From recent discussions within, it seems like that a fourth tier will not materialize. There are simply not enough people (at least not as much as AC hopes) that flies over 200K per year.

They wanted instead to focus on making SE/E/P better. If UA can survive with only 3 levels, there's no reason why AC can't.

One disturbing and serious talk is that upgrades might disappear entirely in favour of having more J seats available as a result of a lot of people complaining of non availability of revenue J seats. There are several people on this board who repeatly complain about this and they might just get their wish.