Yes, but him leading it isn't mutually exclusive w/ being the High King of the Alliance.
On a side note, maybe he'll be the Warchief of the Horde as well
*cue John Cena theme song* "Ladies and gents, please meet the High King of the Alliance, the Warchief of the Horde, the Chosen One, the God Emperor, the General of the Army of Light Anduin Wryyyyyyyn!!!!" *cue applauds*