Additional .NET Assembly Dependencies and Package Manager + .asmdef's

The package manager and asmdefs are a long awaited feature. When it arrives I would almost certainly need to create packages that will require .NET assembly references. Currently you need to modify the mcs.rsp file in the project, but this does not work well when it comes to making module and reusable code.

For example, I would like to make a modular reusable package (Package Manager, when its supported) that would reference System.Reactive.Core, .Interfaces and .Linq.

Can/will a package manifest add a .NET assembly as a dependency?