TfL and Network Rail are seeking the views of Londoners and those in the South East on CrossRail 2. The scheme would alleviate congestion on both TfL and Network Rail routes and support the London/South East economy.
Two possible routes have been identified for the scheme - a Metro and Regional (above) plan.
As TfL say:
In addition to helping London's transport network keep pace with growth, Crossrail 2 would offer benefits to local residents and businesses by offering more direct, fast, frequent services that are not available at present. Passengers would have new travel choices to avoid crowded transport interchanges.
HS2 will greatly increase passenger use of Euston station. A new, Crossrail 2, station at Euston St Pancras would help disperse passengers and reduce the crowding and delay that would otherwise occur at Euston.
The consultation runs until 2 August 2013 - you can give your thoughts here.