The "Generations" mentioned in this talk have been replaced with "Platform Standard".
The old monikers are "dotnet5.1" through "dotnet5.5", and (as of December 2015) these are the only framework monikers recognized by the tooling (i.e., NuGet). The new monikers are "netstandard1.0" through "netstandard1.4"; only the names and version numbers have changed, nothing else. I expect NuGet will soon be updated to understand the new "netstandard" terminology.
The Portable Class Library Profiles page has been updated to include both monikers in addition to the old-style NuGet moniker.