So in the last Q and A Ion confirmed that we will see a 'mage tower' again in future. To define 'mage tower' I mean a tough solo challenge that will provide a reward at the end of it.
He very definitive without giving a timeframe, but I would hazard a guess that it is this expansion and that it will launch in 8.2 for the same reason the previous system launched in 7.2, to allow people two raid tiers worth of content and over one year of time to tackle it by themselves.
The reward will almost certainly be another cosmetic transmog, and almost certainly a weapon for each spec.
So given that, I would like to see the following.
Fire: A staff. Arcane and Frost got beautiful staffs in Legion (particularly frost), and it's fire's turn to get something really, really nifty in the 2h department.
Frost: A one handed sword or dagger plus offhand. I would like something as elegant for Frost here as it's legion staff was, a blade seemingly carved of ice if I had my way.
Arcane: A cool wand and offhand. A wand skin would be thematically appropriate for arcane, and it would be different from the other two.
Those are my thoughts.
Yours?