Like, is there a period of no ranked?
Will it just reset elo?
Will it keep my elo and just put w/l to 0?

Last time I quit in between seasons :/

Elos are reset, so (mostly) everyone has to climb back up the ladder

pre season 3 will begin after the elo reset. You will be able to play ranked, however league will be in off season and season 3 won't begin begin till they announce it followed by a host of game changes.

The elo reset will be a soft reset, meaning 99% will become 1100~1300. and everyone will be within 300 elo of the 1200.

I believe they do soft reset which is (current elo-1200)/2+1200
So if your current elo is 1500 then it will be 1350 when season 3 begins. Not sure if they will replace current elo with high elo.
Yes your w/l will reset to 0 and so will your ranked stats. You can still check out your season 2 ranked stats by clicking a button when viewing your profile.
Doubt they will have a period of no ranked.

There is a few week downtime and they don't fully reset elo. They bring it closer to 1200 based on what you are currently.

Stats for past reasons are put into a tab for that season and aren't displayed with the new season.

when will they reset elo?