No, pet abilities are kept at the level you have summoned pets, even if you switch to lower skill gear.
You can easily check this, take a LK for example with lvl 3 arcane blast: the spell allows 2 projectiles.
Now you resummon the LK while wearing a +1skill gear: the LK will have a lvl4 arcane blast, then you will see 3 projectiles from the LK.
Unequip your +1 skill gear: the same LK will still throw 3 projectiles.
Thats' why mastery shrines are important for petmancers during the leveling.