Battle.Net of North America released the news that Heart of the Swarm would add leveling system in the Beta test.
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.

Read more from: http://bit.ly/VTWN5x