When conveying his knowledge of the future to reinforce that he knew the secret identity of Savitar, the time-traveling Abra Kadabra insisted that he knew who all of The Flash's top adversaries: Zoom, Reverse-Flash and...DeVoe. That last one is probably a clue to who Barry will be tangling with in the show's fourth season as DeVoe likely refers to Clifford DeVoe, aka Thinker.
He's a Golden Age Flash villain who was originally a criminal defense lawyer that came to realize that individually, criminals are not very bright - but collectively, and with someone of greater intelligence providing direction, no single hero should prove their equal. Previously at PaleyFest, executive producers on The Flash confirmed that season 4 would not feature a Speedster as the primary antagonist and Thinker certainly fits that description.
Besides DeVoe, there have been several different incarnation of Thinker, who have all possessed different abilities (such as mental projections and the ability to control machines) making it possible for the show's creative team to cherry-pick from each iteration to make Thinker a more formidable opponent for Grant Gustin's Barry Allen.
Does Thinker sound like an adversary you'd like to see Barry face in season 4? With someone of his ilk calling the shots behind a group such as The Rogues or any other collection of metahumans the Flash has put away over the last 3 seasons, Team Flash might actually need to bolster its ranks!