The Standard rotation will get rid the format of many powerful archetypes, which will open the doors for a new meta-breaker: the Surveil mechanic. Doom Whisperer is clearly the headliner of the Surveil-based cards in Guilds of Ravnica, which can be combined into some disgustingly powerful combos.
Just think about how easy it will be to find cards that you need for the mere cost of 2 life. It is not exactly Brainstorm effect, because you can't draw your cards, but you can order them any way you want, and in this way control your game like never before.
Doom Whisperer is already priced rather high, and if the Surveil decks start winning all the upcoming competitive events, then the price will double up.