The Lich King have been a very iconic lore character in the wow universe, and since we already got Illidan, Deathwing etc , we should already have The Lich King, but this expansion theme sounds perfect to fit him in, and as Illidan and Deathwing, he might become neutral aswell for all classes to use.
Now, that its quite likely that The Lich King might become a card now, is the my doubt for the card text. If you take a look at all the revealed neutral legendaries, all of them got a pretty much same kinda effect, if your deck doesnt include x mana cost card do this do that. Its a pretty boring and bad effect, and I am afraid The Lich King might have something similar.
However, since its likely he will be a high cost card, it could be something not too bad (since the rest legendaries remove our 2-3 mana cards which is very important), like etc if your deck has no 10-mana cost card, equip a 4/3 Frostmourne with *effect*.
Whats your thoughts? Also sorry for terrible english :P