Okay guys, catch me up on League. What do i need to know about season 4?
Supports and Junglers are real champions now rather than mobile piggy banks for the opposite team. Tops are made of beef, mids are made of win, and the meta is slowly leaning toward hyper-carry ADCs again with the realization that "soft" carry ADCs don't actually do much in the resulting meta. (Basically, everyone except the mid has gotten tankier due to top being a tank lane and junglers/supports having actual income, so a non-hyper carry like Ezreal just sort of wet noodles around fights not getting much done.)
The jungle's actually been opened up pretty wide with some of the item changes, even if nobody's really acting like it. There are a lot of AP junglers (even beyond the semi-"rational" ones like Amumu, Fiddlesticks, and Cho'Gath) that are now viable, expect to see the pool open up in the coming weeks as the trend-setters adjust to it.
Mid's back to being a weird mix of assassins (Leblanc, Zed) and zone-control APs (Gragas, Orianna... no Frostbird yet), with the odd siege specialist like Nidalee popping in to say "Hello" now and then.
The fact that supports build actual items early and often has been painful for the squishier supports (who are too vulnerable to all-ins from aggressive supports like Annie and Thresh), but has really opened the door to supports who previously were borderline due to their item dependency, like Leona. A lot of non-traditional supports are also probably viable, though the long history of troll-picking supports makes it hard to tell who's got serious, good ideas and who's just being an Edward.