Link to the news post and the infographic.
So, it looks like Riot pushing out another set of changes to their ranked system, which looks a lot like the system currently in use in StarCraft 2.
Basically, it's going to arbitrarily place you in a group of 250 players. This has no effect on who you play against, but it's supposed to give you a feel of progressing up the ladder. ELO is hidden for all ques and you see these league points instead. To advance a tier, you have to win a best of 3 (so 2 games), and to advance to another ranking you have to win a best of 5 (3 games).
There is also a new ranking, called Challenger that will allow highly ranked 5s teams a chance to go pro.
Edit: Riot did an AMA about it.