Destiny is reworking how their leveling system works in The Taken King, coming September 15.
The short of it is that they will no longer have "light levels." If you don't play Destiny, this probably doesn't mean anything to you, but it basically means that once you hit level 20, you continue to level by collecting better gear and not buy gaining experience points. This was a novel idea, but it is a major factor in why I burned out on the game. It was so frustrating to play some incredibly hard missions and then getting nothing for my efforts because the loot that dropped wasn't good enough.
I can't wait to get The Taken King next month even more now.