Your coins aren't worthless, Poloniex still has them and they can still be burned.  We have no control over how Poloniex conducts it's business or what it announces.  They were contacted multiple times between September (before the process started) and the April  20th deadline and were aware of the changes.  It was their choice as to what action they took with that information.

I have been in contact with Poloniex attempting to help them with the transition and the conversion pool is still active and able to burn coins for conversion, a few of us are still supporting the classic chain with hashes just so Polo can burn their remaining coins.

While I understand your frustration that you can't access your coins at this time, I assure you we are working with them to help resolve this even though the deadline has passed. We want nothing more than for everyone who wants their coins to be converted to have them converted.  It is my hope they will have this resolved in the next 24-48 hours and you will be able to either withdraw your coins as research coins and trade them on another exchange or if Poloniex chooses to open a Gridcoin-Research market buy & sell GRC on Poloniex once again.