So is Cassiopeia going to get more buffs?

I wouldn't hold your breath.

Sej got reworked, nerfed, then never touched again

Olaf got reworked, kinda ish buffed? Then never touched again (well not literally but not anything significant)

Skarner got reworked, buffed, then nerfed worse, then never touched again.

Chances are Cass was put in the 1.99 bargain bin while Riot dusts their hands off from their "Job well done" to move onto the next rework.

No, she is nice. I think she need just +5 damage in her E. I like her.

Cass is actually really good. Reason being is unless she is literally instantly killed every single team fight or the enemy team is super pushing, she will always hit her hyper carry status no matter what because to get there she doesn't need gold, just time and accuracy. Once she hits 400 stacks, she is basically a Magic Damage ADC aka APC that does sustained burst damage. All she needs is boots and a Rabadon's as well since getting just a Rabadon's plus a starting Doran's RIng gives her about 216 AP excluding any runes or masteries. Add that to her 2 second AoE stun and she's a horror. You just have to get the 400 stacks.

Cass isn't in the best spot. Her damage spikes are gated so it's very hard to actually hyperscale even if you do well. You won't hit 400 stacks even if you are dominating your Lane till 30.

That's her real problem.