Metro and Tobu have apparently agreed on a basic design for two upcoming models, the Metro 13000 series and the Tobu 70000 series. These will be used for services that interline between the Metro Hibiya Line and the Tobu Skytree Line. Services are currently operated with a mixture of 3- and 5-door cars; these will all be 20m (sorry Toni) 4-door cars with longitudinal seating, run in 7-car formations. They will come into service from 2016 to 2019. The link below has an image showing the Metro car at top, the Tobu car in the middle, and then the Tobu car's interior at the bottom.
http://railf.jp/news/2015/06/18/100000.html