Riot have been tinkering about with the League of Legends jungle for a while now. The point, as covered in the pre-Worlds press conference, is to make jungling less of a solved problem with only a few viable champions. "The jungle champion pool has been really narrow. We want to see a broader range of junglers in the mix and give those junglers more strategic choices". The company now has a dev blog up explaining the work they've been doing in more depth.
The problem Riot are trying to solve isn't actually just that there are a small number of reliably viable heroes. It's that the games tend to play out very similarly for those heroes because the ways they can be built and played don't vary much in the context of different matches.
As dev Fearless says:
"After a few dozen repetitions of the Lee Sin vs. Kha’zix match up, we as junglers have a very good idea of how the match up will play out, and the game is very likely to feel very similar to the games before and after."
It's a result which runs counter to the point of being a jungler. Junglers are the Champions who are free-est to move around the map and affect the balance of play when they do so. In limiting their viable playstyles you lose that strategic flexibility.
Instead of skewing heavily towards fast-clearing Champions, jungle camps are being reworked to reward mitigation-focused junglers. By this I mean that the camps have been given a base stat increase so champions who can take those down and still be healthy enough to deal with other camps afterwards will be appealing.
The camps will also offer a buff when Smite is used. (Smite being a summoner spell which deals true damage, not the Hi-Rez MOBA of the same name) By knowing which camps give which buffs you can adapt your focus to suit your actions on the map. For example, Gromp – the grump toad guy – gives you poison armour which deals magic damage over time to your attackers and makes you a less attractive target as a result.
A Scuttle Crab minion is also being added to the river as another incentive for champions to leave the jungle at various points. The fact that it runs away from its attackers means it can relocate skirmishes – could be interesting, could be crab MOBA Benny Hill. Possibly both.
Items are also being changed in order to support potentially more diverse playstyles. In addition to the reworked Hunter's Machete there's Stalker's Blade (good for ganking and adding more snowball to snowball lanes), Poacher's Knife (counter-jingling), Skirmisher's Sabre (1v1 power) and Ranger's Trailblazer (safer jungle farming). They're being billed as role-agnostic so to make them more relevant to a particular character you need to add enchantments for particular stats gains.
The basic approach is being described by Fearless and fellow dev Axes as "more scalpels, less sledgehammers". What that means is that lots of different aspects of the game which affect junglers can be tweaked in small ways. The intention is that Riot will be able to fine-tune without accidentally causing wild swings in the meta.
As per usual, these are changes which are being trialled in the public beta environment. As such they might not make it to the full game (or at least not in their exact current form).