Something I just noticed looking at the list of vanguards

(List taken from champion subclass list http://boards.na.leagueoflegends.com/en/c/developer-corner/3A5uuBw7-champion-subclass-list?show=rundown) Vanguards

•Malphite •Amumu •Leona •Zac •Gragas •Rammus •Mega Gnar •Sejuani •Rek’Sai •Sion •Nautilus •Skarner

Skarner is on this list, and riot has said in their skarner follow-up discussion (http://boards.na.leagueoflegends.com/en/c/developer-corner/T5MTYIIt-followup-skarner-juggernaut-update) that they wanted to change him from a juggernaut to a vanguard and had some changes planned, changes that never surfaced.

So it could be likely that Skarner will be part of the vanguard update, possibly one of the bigger changes considering it is a change being done to change his whole subclass (even though he is listed as vanguard, he is still kind of a juggernaut).

The only thing that could hurt his chance is the fact he was part of the juggernaut update so we don't know if riot is willing to have a champ be part of the major changes in 2 class updates.

Even if Skarner isn't included in the major changes however, it is likely we will see changes done to him during this update.