It makes sense Fallout 4 is their next title
Oblivion -- 2006
Fallout 3 -- 2008
Skyrim -- 2011
They seem to alternate between the two series (not taking into account Fallout New Vegas since it´s from Obsidian)
Predicition: it will be released for PS4, NextXbox and PC, there will be no Wii U version.It will come out at the end of 2014.