Diablo 3 desperately wants you to keep playing it, and to that end Blizzard have been running a couple of 'seasons' full of challenges, conquests and of course loot. They've just announced (opens in new tab) that the second is about to end, on April 5th. Wasting no time, they've also announced that season 3 is set to start on April 10th, taking the time to note, in explicit detail, which of your rewards will carry over.
It's basically everything, except the rewards for Conquests, which aren't available for regular heroes (although "your mighty deeds will still be chronicled in the Records page of your profile for you to view at any time!" - yeah cheers Blizzard). Seasonal heroes created for season 2 will be converted to regular ol' Normal or Hardcore heroes, while the seasonal leaderboards will be wiped. There's a lot more detail at that link above.
Season 3 will kick off on April 10th, giving you five days to ruminate on your accomplishments before the whole vicious cycle begins anew. It's likely that the teased patch 2.2.0 (opens in new tab) will be implemented during this downtime, so that it's ready and in place before the new season begins. (Thanks, Blue's News (opens in new tab).)