To preface this: I'm aware of certain threads that have started discussions that apparently got heated enough to spawn troll threads. This is mostly concerning Expert and what-will-no-doubt-be "Level 70 roulette".
While I know the dev team is fond of being formulaic when it comes to making dungeons, I seem to recall Yoshida (or another member) mentioning wanting to try a higher difficulty dungeon. I'm not sure if this was already implemented with Palace of the Dead floors 101+ or if the comment was another musing that's been misinterpeted, but I was wondering if, in a broader sense, there could be an actual "difference" between Expert Roulette and the future "Level 70 roulette".
Currently we have Expert containing the two most recent dungeons, with Level 60 containing previously released dungeons. The end result is Expert seems to lack variety and grows stale quickly while Level 60 roulette can be a surprise (barring it's tendency to fill Aetherochemical Research Facility).
Suppose, though, Stormblood patches implemented two varieties of dungeons at endgame: One that sits at the current difficulty trend, with maybe an occasional boss that may require a bit more effort, and one that is deliberately tuned to be of a higher difficulty, with a return to dungeons having mechanics throughout (my primary example to point to is Wanderer's Palace's tonberry stalkers). Assuming the tomestone currency system is in place, the former dungeon would be worth less the latter.
However, the first variety of dungeon would have a permanent place in Level 70 Roulette, and second in Expert. Assuming two new dungeons per patch, Expert and 70 roulettes would eventually grow to reasonable sizes as patches are implemented.
I am mostly just dreaming here, as I recognize there would be some snags with this:
1. Stormblood release with this model would mean either 2 dungeons and no roulettes, or 4 dungeons for the sake of creating the two roulettes.
2. Development time: Would a more difficult dungeon each patch push patch dates further apart?
3. Complacency setting in looking at the long term: To a degree this is happening now with recent dungeons and raids. There's only so many combinations of mechanics that can be used and re-used before it becomes too familiar to a number of players. How likely would it be that after a few Expert dungeons the playerbase reaches the point where everything is the same again?
I'm not counting any "entitlement" related snags with this, such as Expert being "inaccessible" to some players or rewards being "not enough" for Level 70: Tomestone accumulation seems to be a very rare issue that if Expert is "too much" for some players that Level 70 roulette (along with the other roulettes) will be enough.