Blizzard outlined three major changes yesterday that will affect the endgame progression system. First, there will be no level cap for Paragon levels. Second, Paragon levels will be shared account-wide, with all normal characters sharing levels and all heroic characters doing the same between them. Third, players will get new Paragon points to spend in four categories: core, offense, defense, and utility.
When the expansion goes live, players will receive their new Paragon levels based on the sum of the accumulated Paragon experience on each account. Hardcore heroes who died at 60 will also contribute to this XP pool. Players without the expansion will transition to Paragon XP at level 60, while players with Reaper of Souls will do so after hitting level 70.