Hearthstone's Chadd "Celestalon" Nervig commented on the Arena during today's Reddit AMA and has confirmed they are considering bringing back rotations to the Arena.

Chadd does mention that they may return in "some form" in the next expansion though, exact specifics aren't yet known.

Quote From Chadd Nervig

We love Arena. It has a passionate and dedicated following, and one of the things that we think is most important to Hearthstone is that there are many different ways to play. Our main focus right now has been on developing new game modes, while keeping Arena in a stable place. I can definitely understand wishing for 'something new' (beyond new expansions); are there little changes that you think would help Arena out?

To some of your specific points:

  • Set rotations had some downsides as well (a more complex format, old sets out of place at times balance-wise, etc.). Since they were removed, we’ve seen a large amount of vocal support for them, and are considering bringing them back in some form for the next expansion.
  • Buckets were a mixed bag; we could spend all day tweaking buckets, but we didn’t really see positive results from them. Even just a few poorly-bucketed cards would cause significantly negative community reaction/experience, until we could fix them. They made individual draft picks more interesting, but made decks more same-y over the long term. We think it’s OK to have some easy picks in your draft, and feel like the current drafting still offers interesting choices a lot.
  • Offering rates, particularly on certain extremely powerful cards like Twin Tyrant and Dragonqueen Alexstrasza are mostly tweaked with class balance in mind, so the strongest classes do get less of these powerful cards. In the future, we’re open to removing cards that are too powerful for Arena. We’re considering doing some of this for the next expansion, but Descent of Dragons cards also likely won’t be in the rotation anyway if we do an Arena Set Rotation as mentioned above.