Blizzard announced during their May Developer Update Livestream that there will be no leaderboards in Diablo 4 until Season 3.
Diablo 4 Developer Update – Liveblog Summary
During the March Diablo 4 Group Interview we have learned that leaderboards connected to competitive activities will be added post-launch to Diablo 4.
Diablo IV Group Interview Unveils New Information – Future of Diablo III, Leaderboards, Seasons
If you have played Diablo II: