D4 will have sets just not at launch per Joe Shely. 
“As we’ve been building the game, we felt like we could evolve sets in a new way relative to what we’ve seen in Diablo 3. But, we needed some more time to get them into the game in a way that would work well with the rest of Diablo 4, so you won’t see sets at launch in the game,” Shely explains. “We think sets are cool, and we want to do them right – so that’s something we’re looking at for our live service.”