So the pre-season to LoL has kicked of and not much have changed.
Junglers no get slightly more gold thanks to the Jungle items and the new camp gives them something to do if they want to farm or can´t gank. The jungle will change in difficulty based on your Masteries rather significantly but not as bad as when S3 started.
Masteries are supposedly more "streamlined" for the rolls but in truth they are more restrictive, there is less room for experimentation now than in S2-S3. Out of the different Masteries I believe that defence is the strongest and will be seeing much use for this season.
They will change Runes later in January but they have confirmed that it is happening.
The new items are pretty much exclusively meant for Supports and Junglers to give them more gold, the same goes for the new exp system and other changes to the game.
Trinkets need to be tested and one is right now disabled from the game.
Finally Nasus got a Visual Update + new VA and it looks really good.