Blizzard will release a patch for the StarCraft 2: Heart of the Swarm beta "soon" which will add a new 'Leveling' feature.
Players will be able to test out the new Leveling mechanic - a new progression system which offers rewards to players as they earn XP.How will it work? Here's Blizzard's explanation"
"In the Heart of the Swarm leveling system, players earn experience while playing Blizzard matchmaking modes and custom games on Blizzard maps. You'll earn XP for the race you're playing with each unit you build or destroy. Experience is awarded at the end of the match, and accumulates as you level up from 1 to a maximum level of 20 for each race.
"Getting into the game and playing as much as possible will earn you XP and rewards. Build up powerful armies, wreak havoc on the map, fight to the bitter end, and you'll be rewarded for your efforts! There will also be ways to earn bonus experience points for a match. We're already working on concepts like 'bonus XP for your first win of the day' and 'extra XP when you play in a party with a Battletag or Real-ID friend'. We're considering 'bonus XP weekends' and other sorts of activities, which will be tested in the beta.
"The Leveling system is how you will earn most portraits and decals in Heart of the Swarm. We're creating a multitude of new images for players to collect and display. Your $#@!ulative (Protoss+Terran+Zerg) level will also be displayed right next to your player portrait, so others will be able to easily see how far you've gone in mastering the races of StarCraft II.
"Each level you earn awards either a decal or a portrait for the race that you're playing. These rewards get more and more epic as you progress in a race. The rewards will be different for each race, so truly dedicated players can push themselves to great heights for each of the three races."

http://www.computerandvideogames.com...-add-leveling/