Well there will be players who will attempt to field nothing but vehicles in 8th Edition, think:
Armor Companies or Armor Battalions
Plus there will be a Detachment that would allow them to do this.
I do not think that would be a good force since a Combined Arms approach will always be proven to be better.
Plus except for certain vehicles most vehicles will not last much pass the 2nd turn due to the weapon power that their opponents will be bringing to the table.
Plus if you play on a table that is lacking terrain many would be gone by the end of turn one.
The thing is it will take 2-3 weapons firing at one vehicle.
So the days of you shooting your Tau Railgun and destroying your opponents big nasty vehicle with one shot will be gone.
Plus with the new way shooting Strength against Toughness in 8th Edition a Strength 5 weapon only needs a 5+ instead of the old 6+ to wound and just might come with a -1 Armor save as well.
So Heavy Bolters, Multi-Lasers, Scatter Lasers and Shuriken Cannons are getting a boost and they are all will have multiple attacks.
Oh and Twin-Link is gone as well so expect to see Eldar Warwalkers with dual Scatter Lasers or Shuriken Cannons.
Plus I am interested in just what the Ork Loota weapon will be like because a unit of 10 Lootas will make short work of most vehicles.
The only good thing is that they will be BS 5+.