Poloniex guys only care about big coins that pays them money and they can add to also pump themselves and make money. it is possible that they don't have as much PIVX themselves as they have other coins like Dash or ETH so they are waiting to add it and then pump it properly with the stash they get.
Polo is Pump Central of Altcoins
my understanding is they don't like forks, i honestly don;t see what pivx offers over dash.
a lot more profit! and a lot less centralization and zero premine.
you can pump a coin from 100 satoshi to 0.01BTC
or even 0.1BTC
but as price goes higher the pump gets harder. for example you can't easily pump a coin from 0.05 to 0.1 (a simple 2x rise) but you can pump it from 100 satoshi to 10000 satoshi (a big 100x rise).
Yea I saw the same tweet, so I would expect PIVX and other popular coins to get added soon. Also, is it up to the Developers if their coin gets added?