I'm pretty certain Polo is on the verge of pulling an exit scam. I have hundreds of dollars worth of coins "Awaiting Approval" for withdrawal... for almost 2 weeks now.
Given that crypto is likely in a giant bubble right now, they might not have the funds to process all the withdraws that are taking place.
This is possible but hopefully they wont really do such thing there are already lots of complain from poloniex regarding withdrawal and even deposits on which we can really think off that they might already preparing for an exit scam and withdrawals i guess are piling up on huge amounts already same as you assume. Lets watch out for their next step.