I like Lodash and Underscore. Very useful libraries. I'm not sure how Lodash functions and native functions compare generally speaking other than the obviously different API.
If ES.Next refers to ES9 (ES2018), then I'd say, hopefully: Async generators, public and private fields for classes, rest/spread for properties, and if we're lucky, a whole slew of new RegExp features (look-behinds, named capture groups, Unicode character classes, dot-all) that will make the RegExp writers among us super happy I think. I'm also really excited about BigInts which is a new number type that can only hold integers but can have any precision you want (to see why this is important, try 9007199254740992 + 1 and see what you get).