PIVX is already on Poloniex... it's called DASH. 
Shockingly, some people don't want their DASH with 15% of the total market supply fast-mined in the first few hours, thus PIVX. It'll get added.
Isn't PivX an ICO coin anyway?
PivX needs to prove that it's holders can endure a few months without rocket growth without dumping because the price rise is at this point a bunch of people expecting a polo pump. The coins needs maturing. Look at ZEC as an example of a hype train coin getting on the big exchange too fast. Consider the mass delistings was largely over pump and dumps.