There are a few details coming out now about the new Verminlords along with a couple leaked images. This will give you some insight to the differences between four Verminlords and the Verminking.
Here is a link to the leaked images.
http://eltallerdeyila.blogspot.com.es/2015/01/rumores-reglas-de-los-verminlords.html?m=1
via El taller de Yila
All 5 Verminlords have a 5+ ward and 6 wounds
Deceiver 500pt, must take skitterleap but rerolls cast attempts, -1 to shoot at, has shooting attack
Corruptor 500 pt, must take plague but rerolls cast attempts, paired weapon with asf
Warbringer 550 pt, must take death frenzy but rerolls attempts, paired weapon with doomglaive d3 wound
Warpseer 500 pt, must take warp lightning but rerolls attempts, +1 ward save while he has his orb, orb is a thrown weapon that is a template
Lord Skreetch Verminking is 650, always has 13th and rerolls casting attempts, has 2 weapons 1 asf 1 doomglaive chooses each turn
Stats for all of them vary slightly
There are also a few passages in the WD hinting at Grey Seers summoning Vermin Lords...
The Verminlords kit looks like it is on a square base possibly? Very hard to tell.
Since the Verminlords doesn't choose his plague spell I can take a plague priest and double up on Plague. Nice!
There is also a one page article on "the risk of summoning" vermin lords, and a story when Thanquol tried to summon one & summoned Skarbrand