It seems that the High Elves are getting a new Legend and it is likely that so will the other factions. Here are some guesses for who the new Legends are (assuming they are famous characters):
Dwarfs - A Runelord. Either Kragg the Grim or Thorek Ironbrow.
Empire - We have the top priest, now the top mage. Balthasar Gelt.
High Elf - Not sure. Phoenix King or Everqueen?
Ork- A Shaman or another Warboss. Wurrzag or Gorbad Ironclaw.
Dark Elf - the other witch. Hellebron
Chaos - One of the iconic beastmen characters. Malagor the Dark Omen or Morghur the Shadowgave?