Blizzard has given word that there will be a full ladder reset coming with the release of the v1.13 patch. No ETA yet, and they promise more details before the date, but you might want to start planning your ladder rush now.
Please be aware that with a ladder reset all ladder characters are moved to non-ladder. This means that your characters will still be accessible but will no longer have access to ladder-only features and games. In order to play in the new ladder season after the reset you will need to make new ladder characters.