Basically at the end of the last split there was a mini tournament and 4 of the teams in the LCS are put into relegation matches after they lose.
At the same time, the top 8 amateur teams are picked from the ranked 5s ladder (or something like that) and face off against each other in a best of 3. The 4 amateur teams that win their BO3 face the pro teams in the relegation/promotion matches which is a BO5. The 4 teams that win against their opponent there get promoted to the LCS.
So far only the Copenhagen Wolves from EU have managed to keep their position in the LCS in both EU and NA. There are only 2 matches left, Dignitas vs. Team Summon and CLG vs. Azure Cats (bigfatjiji's team).
Whether you like or dislike CLG, it's going to be really weird if they lose and end up disbanding because they're one of the oldest and probably most famous LoL teams. They were looking really shaky throughout the LCS because they still play like it's season 2 and don't really try to learn new stuff saying that "it won't work for them" because of their playstyle. I mean, HotshotGG still has the same champion pool from 2 years ago LOL @_@
http://leaguepedia.com/wiki/Riot_Lea...mmer_Promotion