Assuming blizzard even releases a new expansion, what classes are you hoping they include in it?
Me personally, my favorite D2 class was the necromancer, everyone use to !@#$% about my skeleton army, but i use to love it.
Other than the necro, my favorite class was the amazon, and the demon hunter is close enough for me.
Yeah amazons were my favorite but i think they need to add a real pet class before anything else.
A pet class is unlikely. It would be broken, given the way this game works.
Right now, there are two playstyles: ranged and melee.
Ranged take a crapton of damage, and get countered by affixes that force them closer. They do a lot of damage, but they do it inconsistently (they need to kite often)
Melee absorb/avoid/resist the vast, vast majority of the damage, and get countered by 'run away' elites (dang insects from Act 2, demon birds from act 3, Morlu Incenerators from act 4), affixes that cause them to lose control of their character (knockback, nightmarish, frozen in small spaces), and affixes that prevent/mitigate damage on the target (Shielding mostly. Somewhat Extra Health, Health Link, Invulnerable.) They do less damage, but they do it very, very consistently.
Pet classes would be broken because their pet would soak the attention and the damage- meaning they wouldn't have to kite like a ranged (they would have 100% uptime on damage), and they wouldn't have to worry about loss of control affixes or 'force closer' affixes.
It would be MUCH easier for Blizzard to design and balance something within the current 2 models.