YouTube Creator Studio combines a lot of useful information about your videos: analytics data, video management, comment management and a dashboard that lets you see what's new. It's available at https://www.youtube.com/dashboard for the desktop. There's also an Android app and an upcoming iOS app.
The Audio Library now includes thousands of royalty-free sound effects you can add to your videos: from dog barking to cowbell ringing, from zombie roar to keyboard typing, alien breath and baby whine. You can download the audio effects as MP3 files and also add them to your favorites.
YouTube will add support for 48fps and 60fps videos. You can test the new feature using this playlist. "We're starting to roll out video support for 48 and even 60 frames per second. See how high frame rates can make motion-intense videos even more awesome," mentions the description.
Fans will be able to contribute money to support a channel. They'll also be able to contribute subtitles. "In the coming months, your fans will be able to submit translations in any language based on the subtitles or captions you've created, helping you reach even more viewers." You can test user-contributed subtitles by checking some of the latest Barely Political videos.
YouTube will also add better-looking annotations and more ways to create playlists.