Что-то все забыли про сабж.

Свеженькое (ну, относительно ) о _возможных_ добавлениях в c#7:

Non-nullable reference types (already working on them)

Non-nullary constructor constraints (require CLR support)

Support for INotifyPropertyChanged (too specific; metaprogramming?)

GPU and DirectX support (mostly library work; numeric constraints?)

Extension properties and static members (certainly interesting)

More code analysis (this is what Roslyn analyzers are for)

Extension methods in instance members (fair request, small)

Unmanaged constraint (requires CLR support)

Mulitple returns (working on it, via tuples)

ISupportInitialize (too specific; hooks on object initializers?)

Statement lambdas in expression trees (fair request, big feature!)

Language support for Lists, Dictionaries and Tuples (Fair; already working on tuples)

Все weekly notes можно найти по ссылке.