https://images.contentstack.io/v3/assets/blta38dcaae86f2ef5c/blt6a486980f42fa6b8/5d9fa5dcf465290ff354b8df/Roadmap_Comp_v13_small.jpg
Closed Beta is coming. I think only the lucky people will get in on phase 1. They explicitly state in phase 2 "More Player Invites" so that's likely going to be where a lot of the non-streamers get a chance to play. Then in Closed Beta they'll flood in more people to try the game. The beta is most likely where a lot of us will actually get a chance and its also going to be the longest phase since they'll need to test things like server stability and bugtest and such.
Still, there's only 10 playable days before Closed Beta and we have no idea when that is or how long it'll last. Assuming the testing periods are indicative of a schedule, sometime in mid January to February is likely when Beta is going to happen. Mid December is when a lot of Rioters are on vacation and it'd be an odd period to release in, and Q1 usually refers to the new year. So it'd likely be sometime between January and Early March for Q1, most likely earlier assuming things are stable.